Basic Pool or Spa Plumbing Systems

Written on:April 10, 2022
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pvc-pipeBasic Pool or Spa Plumbing Systems




Basic Plumbing Systems

To understand the basic plumbing system of a pool or spa, you must follow the path of the water.

The water from the pool or spa, not both at the same time, enters the equipment system through a main drain on the floor, through a surface skimmer, or through a combination of both main drain and skimmer. It travels to a three-port valve (if there is no spa, there will be no such valve) and into the pump, which is driven by the attached motor. From the pump, the water travels through a filter, then to the heater, and back through three-port valves to the pool or spa return lines.


The purpose of the skimmer, as the name implies, is to pull water into the system from the surface with a skimming action, pulling in leaves, oil, and dirt before they can sink to the bottom of the pool, there by providing a conveniently located suction line for vacuuming the pool. Most skimmers today are molded, one-piece plastic units. Older pools have built-in-place concrete skimmers. Some pools have more than one skimmer.

Most skimmers are built into the deck, and are accessed through a cover on top (the cover will be plastic or concrete) or by reaching into the skimmer through the opening that faces the pool itself. Some, as with portable or above ground pools, are separate units that hang on the edge of the pool (in the water or outside of it). Redwood hot tubs use a flat, vertical skimmer that has no basket but skims the surface and pulls any floating debris to a plastic screen. Some portable spa skimmers have a cartridge filter built in. Some pool skimmers include automatic water level controls and automatic chlorinators.

The water pours over a floating weir that allows debris to enter, but when the pump is shut off and the suction stops, the weir floats into a vertical position, preventing debris from floating back into the pool. Some skimmers have no such weir and use a floating barrel as part of the skimmer basket. The purpose of the basket is to collect leaves and large debris so they can then be easily removed. The disadvantage of both types of weirs is that leaves can cause them to jam in a fixed position, thus preventing water from flowing into the skimmer. When this happens, the pump will lose prime and run dry, causing damage to its components. Therefore, during windy periods it might be better to remove the weir from the skimmer to prevent such problems.

By the way, you should exercise care when working around the skimmer when the pump is on. Keep small objects away from the skimmer opening when the basket is removed and especially keep your hands from covering that suction hole for it may be dangerous. You may invariably end up clogging the pipe at some turning point where leaves, hair, and debris later catch and close off the pipe completely.

There are two types of skimmer plumbing. The first one has a single visible suction port or opening. Actually the pipe from the main drain and the pipe from the skimmer connect just below the visible opening and a combination diverter is inserted to regulate the amount of suction from one or the other. A neck on the diverter extends up from the skimmer bottom for attaching your vacuum hose when cleaning the pool.

The value of this system is that when vacuuming the pool, you can divert all of the pump suction to the skimmer bottom, in effect, shutting off the main drain. The diverter also has a nipple aligned horizontally to the opening. Usually when the nipple faces away from the pool, the flare on the bottom of the diverter closes the main drain pipe and all of the suction from the pump is now at the skimmer. When the nipple faces toward the pool, the body of the diverter closes the pipe from the skimmer and all of the suction is now at the main drain. Choice between these two settings will divide suction between the skimmer and main drain.

Depending on needs a pool has its own settings. For example, if the pool gets more leaves than dirt, the diverter should be set to make the suction in the skimmer stronger than in the main drain. That will help the skimmer pull the leaves into the skimmer basket. If the pool tends to get more dirt or sand than leaves, the diverter should be set to strengthen the main drain suction. When dirt falls to the bottom of the pool, the strong suction from the main drain will pull the dirt toward it. This is also helpful when brushing the pool bottom, because suspended dirt will be pulled into the main drain.

Diverter units are made of plastic or bronze. The bronze diverter are heavier and better than the plastic ones. If the suction from the pump is not strong, the plastic ones tend to come loose and float out during vacuuming . They also tend to rotate in the skimmer as you work, changing the amount of suction in the skimmer from what you have set.

The other type of skimmer plumbing has two separate ports, one pipe that goes directly to the main drain or to an equalizer line, while the other goes directly to the pump. Usually the port farthest from the pool edge is the pipe that goes to the pump, and the port closest to the pool goes to the main drain or equalizer line. An equalizer line is simply a pipe that extends from the skimmer bottom down 18 to 24 inches and through the pool wall just below the skimmer. In this type of skimmer, a diverter plate regulates the suction between the main drain and the skimmer.

In both styles of skimmer, the idea is that if the pool runs low on water, the pump can pull water from the bottom of the pool via the main drain instead of the empty skimmer, or from the side of the pool below the skimmer in the case of the equalizer line, so the pump will not run dry.

Some older (often concrete) skimmers have odd-sized ports that can’t accommodate your vacuum hose. In these cases, a special cover plate can create a generic adapter.

Main Drains

The main drain has one or more plumbing ports. One port feeds a pipe to the pump. In a spa, there might be several ports for several pipes leading to different pumps (for jet action).

Another port is a one-way valve or the check valve that allows water that might collect under the pool to enter the pool, but no water can flow out. Water collecting under the pool creates extreme upward pressure that can crack the pool. This pressure, called hydrostatic pressure, is relieved by this valve.

Hydrostatic pressure is an important consideration when planning to drain a pool for any reason. Obviously it is not wise to drain a pool completely during the rainy season or if there is any other suspicion of groundwater.

In some spas, there might be more than one main drain so that if one becomes covered with a foot or hand, water is pulled from the other, avoiding injury to the bather. These drains are usually located at least 12 inches apart. Because spas are relatively shallow, strong suction can create a whirlpool effect. To prevent this, many spa main drains are fitted with anti-vortex drain covers which are slightly dome-shaped with the openings located around the sides of the dome.

Obviously in a pool where the main drain is very deep, this is not a concern, so safety suction lines are not added. Also, the suction in a pool is usually divided between the main drain and the skimmer, so one is not dangerously stronger than the other. Pool main drain covers are flat with the openings on top. The drain area is covered by a grate, usually 8 to 12 inches in diameter that screws or twist-locks into a ring that has been plastered into the pool bottom.

General Plumbing Guidelines

Before proceeding to specific instructions on working with PVC plastic, galvanized, or copper plumbing, here are a few general guidelines that should be taken into consideration, regardless of the material you are using.

Measure the pipe run carefully, particularly if you are repairing a section between plumbing that is already in place. In measuring, remember to include the amount of pipe that fits inside the connection fitting, usually about 1-1/2 inches at each joint.

When working on in-place plumbing, support your work by building up wood or bricks under the pipe on each side of your work area. This prevents vibration as you cut, which can damage pipes or joints further down the line. Also, unsupported pipe sags and binds when you cut it. That is, as you cut, it pinches the saw blade making cutting difficult.

Threaded fittings are obvious and simple; however to prevent leaks from occurring in these connections, carefully cover the male threads with PTFE tape and tighten the fitting as far as possible without cracking. PTFE tape fills the gaps between the threads and prevent leaking. Apply the tape over each thread twice, pulling it tight as you go so you can see the threads. Apply the tape clockwise as you face the open end of the male threaded fitting. If you apply the tape backwards, when you screw on the female fitting, the tape will skid off the joint.

Another method of sealing threads is to apply joint stick or pipe dope. Joint stick is a stick of a gum-like substance that works like PTFE tape. Rub the joint stick over the threads so that the gum fills the threads. Apply pipe dope the same way. The only difference is that dope comes in a can with a brush and is slightly more fluid than joint stick. The key to success with joint stick or pipe dope is to apply it liberally and around all sides of the male threaded fitting, so that you have even coverage when you finally screw the fittings together. Some product will ooze out as you tighten the fittings together, but that proves that you have applied enough. If you use dope or stick, be sure it is a non-petroleum-based material. Petroleum-based products will dissolve plastic over time, creating leaks.

A hacksaw or a pipe cutter can be used for cutting the pipes. Pipe cutters are adjustable wrench-like devices that have cutting wheels and are made for cutting PVC or metal pipes. You lock the device around the pipe and rotate it, constantly tightening it as you go, until the pipe is cut. They provide the straightest, cleanest cut of all. A hacksaw can do the work faster if it has fresh blade attached to it.

PVC-Plumbing-FittingsPVC Plumbing

Pool plumbing is prepared with plastic or metal lengths of pipe and connection fittings that join those lengths together. The pipe acts as the male which fits and is glued into the female openings of these connection fittings. Alternatively, connection is made by each side having threads, joined by screwing them together. The plastic pipe used is PVC (polyvinyl chloride) and it is manufactured in a variety of different strengths depending on the intended use.

To help identify the relative strength of PVC, it is labeled by a schedule number; the higher the number, the heavier and stronger the pipe. Pool plumbing is done with PVC schedule 40.

PVC is designed to carry unheated water (under 100 degrees F). CPVC is formulated to withstand higher temperatures for connection close to a pool or spa heater.

All pipe is measured by its diameter, expressed in inches. Typically pool plumbing is done with 1/2- or 2-inch pipe, referring to the interior diameter (the diameter of the pipe that is in actual contact with the water). The exterior diameter of the pipe is more related to the wall thickness depending on the material.

All pipe is connected with fittings. Fittings that allow connection of pipe along a straight run are called couplings, at right angles are called 90-degree couplings or elbows, 45-degree angles, T fittings, and a variety of other formats. In the case of PVC, such fittings are most often smooth-fitted and glued together called slip fittings.

Some fittings are threaded (called threaded fittings) with a standard plumbing thread size so they can be screwed into comparable connecting fittings in pumps or other plumbing parts. National Pipe Thread (NPT) standards are used in the United States so different products of various materials by different manufacturers will all work together. The NPT standard includes a slight tapering between the male and female connections. The importance of this is that because of this taper, it is easy to over tighten plastic threaded fittings and crack them. Great Britain, Europe, and Asia not only operate on metric measurements, but also have their own unique thread standards. Fittings with male (external) threads are called mip and fittings with female (internal) threads are called fip. If one side of the fitting is mip and one side is slip, you order it as mip by slip, and so on.

In most cases with pool and spa plumbing, the long runs of pipe will be underground. Sometimes, however, horizontal runs will be under a house or deck or over a slope where support is needed. in this case, pipe should be supported every 6 to 8 feet, hung with plumber’s tape to joists or supported with wooden bracing. PVC does not require support on vertical runs because of its stiffness, but common sense and local building codes might require strapping it to walls or vertical beams to keep it from shifting or falling over. Remember, the pipe becomes considerably heavier when it is filled with water and might vibrate along with pump vibration.


The supplies and tools you need for PVC plumbing are: Hacksaw with spare blades (coarse: 12-18 teeth per inch); PVC glue and primer; Cleanup rags; Fine sandpaper; PTFE tape or joint stick.

Plumbing Methods

The concept of joining PVC pipe involves welding the material together by using glue that actually melts the plastic parts to each other. In truth, each joint will have an area that is slightly tighter than the rest. In the tightest parts, this welding actually occurs. In the remainder, the glue bonds to each surface and itself becomes the bonding agent. Obviously the strongest part of each joint is the welded portion; but in either case, the key is to use enough glue to ensure total coverage of the surfaces to be joined.

Following is the correct procedure for plumbing with PVC:

1.Cut and dry fit all joints and plumbing planned. Dry fitting ensures the job is right before gluing. If you need the fitting and pipe to line up exactly for alignment with other parts, make a line on the fitting and pipe, with a marker when dry fitting so you have a reference when you glue them together.
2.Lightly sand the pipe and inside the fittings so they are free of burrs. The slightly rough surface will also help the glue adhere better.
3.Apply a preparation material, called primer, to the areas to be joined before gluing. Some PVC glues are solvent/glue combinations and no primer is required. In some states, however, use of primer might be required by building code, so check that before selecting an all-in-one product. If you are using primer, apply it with the swab provided to both the pipe and the inside of the fitting. Read and follow the directions on the can.
4.Before gluing, be ready to fit the components together quickly because PVC glue sets up in 5 to 10 seconds. Apply glue to the pipe and inside of the fitting.
5.Fit the pipe and fitting together, duplicating your dry fit, and twist about a half turn to help distribute the glue evenly, realigning the lines drawn on the pipe and on the fitting. If using flexible PVC, because it is made by coiling a thin piece of material and bonding it together, do not twist it clockwise. This can make the material swell and push the pipe out of the fitting.
6.With rigid PVC, hold the joint together about a minute to ensure a tight fit; about two minutes with flex PVC. Although the joint will hold the required working pressure in a few minutes, allow overnight drying before running water through the pipe to be sure.


1.Make all threaded connections first, so if you crack one while tightening it can be easily removed. Then glue the remaining joints to the threaded work.
2.When cutting PVC pipe, hacksaw blades of 12 teeth per inch are best, particularly if the pipe is wet (as when making an on-site repair). Finer blades will clog with soggy, plastic particles and stop cutting. In all cases, the key is a fresh, sharp blade. For the few pennies involved, change blades in your saw frequently rather than hacking away with dull blades-you’ll notice the difference immediately.
3.No matter how careful you are, you will drip some glue on the area or yourself. Always carry a supply of dry, clean rags to keep the work area clean of glue.
4.Try to make as many free joints as possible first. By that I mean the joints that do not require an exact angle or which are not attached to equipment or existing plumbing. The free joints are those that you can easily redo if you make a mistake. Do the hard ones last-those that commit your work to the equipment or existing plumbing and cannot be undone without cutting out the entire thing and starting over.
5.Use as much glue as you need to be sure there is enough in the joint. It’s easier to wipe off excess glue than to discover that a small portion of the joint has no glue and leaks.
6.Flexible PVC is the same as rigid, but when you insert the pipe into a fitting, hold it in place for a minute or longer because flex PVC has a habit of backing out somewhat, causing leaks.
7.In cold weather, more time is required to obtain a pressure-tight joint, so be patient and hold each joint together longer before going on to the next.
8.Bring extra fittings and pipe to each job site. Bring extras of the types you expect to use, as well as types you don’t expect to use, because you just might need them. Bring extra glue, sandpaper, and rags too.

Copper Plumbing

Copper plumbing is more difficult to install and repair, and it has become extremely expensive in recent years, so copper plumbing is quickly being replaced by PVC. Unlike PVC, copper plumbing will corrode, especially in the presence of caustic pool and spa chemicals moving at high speed and under pressure through the pipes.

Copper was more recently still in use where dissipation of heat was important, such as in plumbing directly connected to the heater. Stainless steel heat risers and threaded galvanized plumbing have replaced that function, making copper plumbing for pools and spas obsolete. Copper is still widely present in various older installations. Copper pipe and fittings look similar to those made of PVC and come in similar sizes and fitting types.

Copper pipe is made in three thicknesses, designated by the letters K (thick wall), L (medium), and M (thin). Most pool plumbing is done with L (medium thickness) material.


The supplies and tools you need for copper plumbing are: Hacksaw with spare blades (fine: 32 teeth per inch); 50/50 solid wire solder; Flux with application brush; Emery cloth or fine steel wool; Butane torch.

Plumbing Methods

Be sure to read the general plumbing guidelines section and the one on PVC plumbing because some of the commonsense methods apply to copper work as well.

Following is the correct procedure for plumbing with copper:

1.Clean pipe and fittings. Start by cutting and dry fitting all intended connections, then clean the ends of the pipe and inside the fittings with the emery cloth (or fine steel wool), sanding until the copper is shiny and bright. Apply a thin coating of flux to the pipe and inside the fitting with a small, stiff brush, coating the entire area where you want solder to make a connection.
2.Fit the parts together and twist a half turn to evenly and thoroughly distribute the flux. Heat the joint with your torch, moving the flame back and forth and around the joint area to distribute the heat evenly until the flux starts to bubble. Be sure the entire joint is hot. A good way to know is to keep touching the solder to the joint until it melts. When it does, you have the right temperature.
3.Touch the solder to the joint. Solder with lead melts and flows more easily. Recently many states have restricted the use of lead in solder, at least when soldering plumbing that is used for drinking water, so it might not apply to pool installations in your state. 50/50 (50 percent lead, 50 percent amalgams) works best, but if no-lead solder is used, even more heat must be applied and maintained during the soldering operation to ensure melting and even distribution. Apply solder to the fitting while continuing to heat the joint, about an inch behind the joint. Solder is drawn toward the heat. The solder melts and enters the joint wherever there is flux, drawn in by capillary action, forming a seal. Work around the joint, making sure solder is drawn into the entire joint.
4.Clean excess solder away with a damp cloth before it cools; but be careful, the heat turns the moisture on the rag to steam which burns you worse than grabbing the hot pipe directly. Allow the work to cool.

Two last items relating to copper plumbing. First, threaded fittings are handled like PVC threaded fittings (see previous section) using pipe dope or PTFE tape to ensure leak-free connections.

Second, another type of copper connection fitting is the compression fitting. This fitting is used in small diameter (1/4- to 1/2-inch) pipe, often inside the heater. The compression nut is placed on the pipe followed by the compression ring. The pipe is placed inside the opposing fitting and when the nut is screwed onto that fitting, the compression ring tightens around the pipe and seals it.

1.Copper pipe is cut with a hacksaw like PVC. Use fine blade for copper (at least 24 teeth per inch or preferably 32) as it cuts faster with each stroke.
2.When making several connections with various fittings, sweat as many joints as possible while they are not connected to the equipment (just like the free joints I mentioned in the PVC section). This way, I can test each joint as it is completed. Hopefully only one or two joints will then have to be soldered in-place and trusted to the luck and skill of the work. To check if the joint is leak free, hold the work with one hand over one end of the pipe or fitting and blow hard through the other open end. No air should escape through the joint-if air doesn’t leak, neither will water. When sweating a joint attached to equipment or other in-place plumbing, the only leak testing will be when the job is complete and the system is checked with water.
3.Solder will not seal if there is any moisture. If you must solder where some water is weeping from a pipe connected to equipment, stuff the line with bread to absorb the water. When the system is turned on again, the force of the water will break down the bread and allow it to be filtered or removed.
4.Most leaks in sweating are caused by moisture, overheating the joint, and most of all, unclean pipes or fittings.
5.Unlike PVC, sweating can be undone if you need to repair a bad job or take old work apart to perform new installations or add-ons. Apply heat to the joint, just as in sweating, until the solder melts and pull the joint apart. If you intend to reuse the fittings or that part of the pipe, carefully clean and sand the copper to a good shine before reuse.
6.Read the directions on the torch, the can of flux, and the spool of solder. Sometimes reading another person’s directions for performing the same task will make more sense than mine. Don’t worry, I won’t be offended, as long as your work doesn’t leak. Also, labels can provide helpful hints that make for better, quicker jobs.
7.When supporting copper pipe to joists for long horizontal runs, use plumber’s tape every 6 to 8 feet as with PVC, but wrap the pipe in that spot with insulating tape first. If you fail to do this, the different metals (copper pipe and galvanized plumber’s tape) will cause electrolysis, corrosion, and leaks.

Galvanized Plumbing

Galvanized means iron pipe that has been coated with zinc or other alloys to prevent corrosion. You will encounter galvanized plumbing in some installations. It is inferior to PVC and copper because it is heavier and more difficult to use. Because the interior surface of the pipe is rougher, it takes, for example, a 3/4-inch galvanized pipe to carry as much water (at the same pressure) as a 1/2-inch copper or PVC pipe. The rough surface also promotes calcium buildup inside the pipe.

Galvanized plumbing can only be joined by threading the pipe ends and fittings and screwing them together. There is no simple sweating or gluing method as with copper or PVC, so exact lengths and threading must be accomplished. However, it does make an easy heat dispersal pipe for plumbing directly to the heater. As shown, you can use a threaded galvanized nipple to thread directly into the heater and then continue with PVC beyond that, also threaded directly to the galvanized nipple. As with threaded PVC or copper, use plenty of PTFE tape or pipe dope and tighten the connections adequately. If connecting threaded PVC to galvanized, apply PTFE tape and join as discussed previously.

If connecting galvanized to copper, you must use a special union called a dielectric fitting. Because of the different properties of the two metals, if they are connected directly, they will corrode each other through electrolysis. The dielectric union connects the two metals while shielding each from the other. You probably won’t use many of these, so if you need one, ask at your plumbing supply house for more details.

Miscellaneous Plumbing

Sometimes in tight quarters or for temporary connections you can use rubber connection fittings called mission clamps, balloon fittings, or no-hub connectors. These fittings are handy for connecting pipes of different sizes or types, clamping directly onto the pipe or fitting without gluing, threading, or sweating. The hazard is that these can leak, wear out, or fail under extreme pressure as when there is a restriction in the system from debris or a dirty filter.

Sizing of Plumbing

Most building codes restrict the speed of flow through pipes to prevent stripping, breakdown, and erosion of the pipe material. Typically water may not move faster than 8 feet per second through copper pipe, and 10 feet per second through PVC. Suction pipes of any type are typically restricted to 8 feet per second.

Obviously the larger the pipe, the better. There is less restriction and therefore less strain on all equipment and plumbing. Use the largest diameter pipe and fittings you can for the job.

Typically pool and spa equipment is already built and plumbed for 11/2- or 2-inch plumbing, and while you can adapt 2-inch pipe to a pump that is designed for 11/2inch fittings. The considerations in all cases are:

Desired flow rate of water (measured in gallons per minute), Length of plumbing runs, Number and angles of connection fittings, Pump efficiency and capacity, and Equipment and restrictions after the pump.

Advanced Plumbing Systems

Advanced plumbing systems includes automated valves, reverse-flow heating, solar heating, and the use of new materials. Let us discuss some of the more common applications of advanced plumbing and the maintenance of these systems.

Manual Three Port Valves

The three-port valve is often used when a pool and spa share one filter, heater and pump. In this situation, the water is alternately diverted to the pool or spa. Spas use the three-port valve to divert air bubbles and jet water to one side of the spa or the other, or the combination of both. The design of three-port valves is such that water flow from one direction and divides it into a choice of two other directions or the other way round. To understand it more clearly, picture a Y, for example, with the water coming up the stem, then a diverter allows a choice between one of two directions, or a combination thereof. Conversely, the water flow might be coming from the top of the Y, from two different sources, and the diverter decides which source will continue down the stem or mixes some from each together.

Manufacturers have different valves based on the same concept. And keeping these valves well lubricated is best for it maintenance.


Since the three port valves are used when the water is shared between the pool and spa, they are designed to take water flow coming from one direction and divide it into a choice of two other directions. They are like letter Y or T. A handle placed on top of the valve turns the diverter 180 degrees in either direction, directing the flow and mixture of water that passes through the circulation system.

Several manufacturers make three-port valves, in Noryl plastic (a type of PVC) or brass, but the concept is the same with them all.

The suction line from the pool enters one arm of the valve body; suction from the spa enters the other. The diverter between the two arms determines which line is connected with the stem, from which the water continues to the pump. Conversely, when the water leaves the equipment, it passes through another three-port valve. The water this time passes up the stem and the diverter determines if the water flows to the arm plumbed into the pool return or the one plumbed into the spa return. By setting the diverter equally between the two, water from each side is mixed.


A valve with the diverter that is surrounded by a custom-made gasket so that no water can bypass the intended direction, is called a positive seal valve.

Some valves, have no such gaskets and, are designed more like a shovel head than a barrel. These divert most of the water in the desired direction with a lesser amount going in the other direction. These are called non-positive valves.

The diverter is held in the valve by a cover that screws to the housing with sheet metal screws, and is sealed with an 0 ring to make it watertight.

Besides the four screw holes in the cover and housing, there is a fifth hole in the cover. This is to ensure that the cover lines up properly with the housing, because on the underside of the cover are specially molded stops. A small screw on top of the diverter hits these stops molded into the underside of the cover. This allows the diverter to be turned only 180 degrees in either direction, ensuring only one side opening.

This screw is removed when the valve is motorized because the motors only rotate in one direction and are already precise in stopping every half-turn. Small machine screws hold the handle on the shaft. A hole in the center of the cover allows a shaft from the diverter to attach to the handle for manual operation of the valve. To make the shaft hole in the cover watertight, two small O-rings slide on the shaft in a groove under the cover.

Maintenance and Repair

As there are simple parts involved, the three port valves are very easy to handle.


Like any other PVC fitting, Noryl three-port valves are glued directly to PVC pipe using regular PVC cement . Avoid too much glue, as excess glue can spill onto the diverter. Excess glue can dry into hard and sharp mass, which may create leak when turning the diverter, there by cutting the gasket.

Brass valves are sweated onto copper pipe like any other fitting. Remove the diverter when sweating so the heat doesn’t melt the gasket.


Lubrication is most important measure to take when it comes to maintaining a three-port valve. The gasket must be lubricated with pure silicone lubricant. Most other lubricants are petroleum based and can dissolve the gasket and can create leaks.

Lubrication should be done when operation feels stiff or at least every six months. This twice a year lubrication is important , especially for motorized valves, because the motor will strain against old, sticky gaskets until the diverter and shaft break, or the motor burns out completely.

To repair a sticky valve from the diverter; firstly disassemble the valve by unscrewing and removing the handle. Then unscrew and remove the cover. Pull out the diverter. Replace the broken diverter and also change the old gasket. Now apply the lubricant liberally and reassemble. Check the diverter by twisting it back and forth several times, there by lubricating the whole unit.


Common problems with three-port valves are the leaks. Before starting the repair works, check its location in relation to the pool or spa water level. If it is below the water level, first shut off both the suction and return lines for opening the valve will flood the area. If installations are made below water level, they are usually equipped with shutoff valves. You will need to reprime the system after making repairs.

The valve will sometimes leak from under the cover. Either the cover gasket is too compressed and needs replacement or the cover is loose. The cover is attached to the Noryl valve housing with sheet metal screws. If tightened too much, the screw strips out the hole and you will be unable to tighten it. The only remedy is to use a slightly larger or longer screw to get a new grip on the plastic material of the housing. Be sure to use stainless steel screws or the screw will rust and break down, causing a new leak. If new screws have already been used and there is not enough material left in the housing for the screw to grip, you must replace the housing.

Leaks also occur where the shaft comes through the cover. Remove the handle and cover and replace the two small O-rings. Apply some silicone lubricant to the shaft before reassembly. This lubricates the operation of the valve, decreasing friction that can wear out the O-rings. The lubricant also acts as a sealant.

Leaks can occur where the pipes join to the housing ports. In this case, the only solution is replacing the housing.

Leaks can also occur inside the valve with no visible external evidence. Water is not completely diverted in the intended direction, but slips past the diverter seal to the closed side of the valve. The symptom will be a spa that drains or overflows for no reason. The cause might be a diverter that is not aligned precisely toward the intended port. Remove the diverter and make sure the shaft has not separated or become loose from the diverter.

With a motorized unit, be sure the motor is clean, free of rust, and able to turn its precise one-half turn each time. The other and most usual cause, however, is that the diverter gasket has worn out or become too compressed to stop all water from getting past. Replace it. It takes very little deterioration or compression to cause these bypass-type leaks. Again, lubricate the gasket well before reassembly for smooth operation and because the lubricant acts as a sealant.

Bypass leaks also result when the diverter itself has shrunk or warped. This sometimes happens when the spa water is very hot or the system ran dry and overheated. Such shrinkage if difficult to see, and does not have to be extensive to cause a bypass leak.

Motorized/Automated Three Port Valve Systems

When small motors are mounted on the valve in place of the manual handle, for automatic or remote operation, makes them motorized or automated three-port valves.


The pool or spa equipment are usually located away from the pool and spa. Some builders place the manual valves near the spa rather than in the equipment area for convenience. The value of motorization is based on the concept so as to locate the motor switch with the equipment and operate it with a remote control unit. The remote might also have other functionalities like lights, spa booster motors and blowers, or other optional accessories.


A manual valve can be motorized and the wiring diagram are provided with each type of valve motor. To motorize an existing valve, the handle and the screws, holding the cover in place are removed. A mounting bracket is set on top of the cover and slightly longer sheet metal screws, are used to refasten the bracket and cover, to the housing. These longer screws are provided with the motor bracket kit. The machine screws that normally hold the handle in place are left on the shaft. The motor unit mounts on the bracket, held in place by two screws, and the motor shaft slips over the diverter’s shaft. The two shafts are secured together by tightening the screws of the diverter shaft. Wiring diagrams are provided with each type of valve motor and they are designed to operate on standard 110 volt, 220 volt, or from an automated system that has been transformed to 12 or 24 volts.

Maintenance and Repair

The problems of the motorized valves are same as that of manual valves.

As mentioned, if the valves are not properly lubricated or become jammed with debris, the motor will continue to try to rotate the valve, finally burning itself out.

If the motor has burned out, using an electrical multimeter, verify that current is getting to the motor. Obviously if there is no current, the problem is in the switch or power supply and probably not the motor. If you are not familiar with basic electricity, call an electrician to help you.

If current is present, remove the motor unit from the valve and try to operate the system. if the motor rotates the shaft normally, then the problem is a stuck valve and not a burnt motor. Repair the valve as described in the previous section.

If the motor is burnt out, it can easily be replaced without replacing the entire unit or valve.

Also check the screws for rust and for becoming loose. For another problem that can occur with motorized valves is that if the mounting bracket or screws holding the unit together become loose, the unit will not align correctly with the valve. So though the motor will rotate its 180 degrees, but it will not fully rotate the valve diverter to match. The solution is to tighten all hardware and replace any rusted screws.

Reverse Flow and Heater Plumbing

Sometimes a system with far more valves and plumbing can reverse the flow system. First thing is to observe the normal operation and mark the pipes and valves with a marker. When you are sure of the correct flow pattern that is, from the pool or spa, through the equipment, and back to the pool or spa: simply turn on the heater and observe it again.

If it is a reverse flow system, remove the excess valve motors to disable the system. Don’t try to leave the units intact and simply disconnect the wiring. This might also disconnect the heater on/off or pump switches that are associated with the remote control system. It is easier to manually remove the motors while leaving the valves in a normal circulation position, clip off and cap the wiring to those motors, and leave the rest of the unit as is.


When you remove a particular piece of equipment that is plumbed into the system, you must cut out the plumbing and replumb upon reinstallation. But concept of the union is that when you need to repair or replace a pump, filter, or other equipment you need only unscrew the plumbing and reinstall it. Union allow you to easily remove and replace equipment without doing any new plumbing.

Unions, like other plumbing, are made of plastic or metal in standard diameters and are adapted to plumbing like any other component. In a typical plumbing union, a nut is placed over the end of one pipe, then male and female fittings called shoulders are plumbed onto each end of the pipes to be joined. The joint is made by screwing the nut down on the male fitting. PTFE tape or other sealants are not needed as the design of the union prevents leaking.

Unions are made for direct adaptation to pool and spa equipment, where the pipe with the nut and female shoulder is male-threaded at its other end for direct attachment to the pump, filter, or any other female threaded equipment. Then, only the male shoulder need be added to the next pipe and the piece of equipment can be screwed into place.


Gate and ball valves systems are seen where the equipment is installed below the water level of the pool. They are designed to shut off the flow of water in a pipe and are used to isolate equipment or regulate water flow. It prevents flooding when you open or remove a piece of equipment or plumbing for repairs. Before the development of three-port valves, shutoff valves were used on each pipe to manually determine water flow from and to pools and spas, in the older plumbing system.

The gate valve and the ball valve are the two types of shutoff valves. The gate valve has a disc-shaped gate inside a housing that screws into place across the diameter of the pipe, shutting off water flow. A variation of this is the slide valve, where a simple guillotine-like plate is pushed into place across the diameter of the pipe.

The other design is the ball valve, where the valve housing contains a ball with a hole in it of similar diameter as the pipe. A handle on the valve turns the ball so the hole aligns with the pipe, allowing water flow, or aligns across the pipe, blocking flow. In each of these designs, flow can be controlled by degree as well as total on or total off.


The gate valve is operated by a handle that drives a worm screw-style shaft inside a threaded gate. If the gate sticks from obstruction or rust and too much force is applied to the handle, the screw threads will strip out, making the valve useless. The valve cap, also called the bonnet can be unscrewed and the drive gear and gate can be removed and repaired or replaced without removing the entire valve housing. Most plumbing supply houses sell these replacement guts, but the parts from one manufacturer are not interchangeable with another.

The packing gland prevents leaks where the shaft enters the valve body. If leaks occur here, the packing material can be replaced by unscrewing the cap nut, removing the old twine and rewinding new twine. Sometimes just tightening the cap nut will stop the leak, but it also tightens the packing material on the shaft, making it more difficult to turn. Plastic gate and ball valves use O-rings to prevent leaks in this location.

Check Valves

The purpose of the check valve is to check the direction of water flow. The check valves have multipurpose uses, and the common ones are listed below.

To keep hot water from flowing back into the filter they are used in heater plumbing.

They are used in the spa air blower plumbing. To check the flow of water and make sure that only air is blown into the pipe and into the blower machinery.

To keep the flow of caustic chemicals moving in the desired direction, with chlorinators.

When the pump is located above the pool water level, check valves are placed in front to keep water from flowing back into the pool when the pump is turned off.

There are two types of check valves, a flapper gate type and a spring-loaded gate type. The flapper style opens or closes with water flow, while the spring-loaded style are designed to respond to certain water pressure. Depending on the strength of the spring, it might require one, two, or more pounds of pressure before the spring-loaded gate opens. As with other valves, check valves are made of plastic or metal in standard plumbing sizes and are plumbed in place with standard glue, thread, or sweat methods.

The flapper-style valve is simple in design and working. It must be installed with the hinge of the flapper on top. If it is installed on the bottom, gravity will pull the flapper open all the time. Sometimes with metal flapper check valves, as the flapper opens and closes you can hear them chatter, particularly if there is air in the system. This is not a malfunction or a problem of the valve. With the metal flapper, the gate may come off the hinge due to rusting. The valve then must be replaced.

All check valves clog easily with debris, remaining permanently open or permanently closed. Because of the extra parts inside a spring-loaded check valve, they are more prone to failure from any debris allowed in the line. If the valve is threaded or installed with unions, it is easy to remove it, clear the obstruction, and reinstall it. Another solution is to use the 90-degree check valve. This valve allows you to unscrew the cap, remove the spring and gate, remove any obstruction, and reassemble.

Be careful not to over tighten the cap-they crack easily on older models; newer models are made with beefier caps to prevent this problem. These units have an O-ring in the cap to prevent leaks. It is wise to clean these out every few months and lubricate the gate, using silicone lubricant only.

Solar Heating Systems Plumbing

Plumbing for solar heating is no different from other pool and spa plumbing. It is located between the filter and the heater, so water going to the solar panels is free of debris and is available for solar heating.

A thermostat on the solar panel determines the water temperature. The water coming out of the filter goes to a three-port motorized valve which sends the water to the solar panels for heating and returns it to the plumbing that enters the heater. The heater thermostat senses the temperature of this solar heated water and if it is still not as hot as desired, the heater will come on to heat it further before returning it to the pool.

Therefore a main component of solar heat plumbing is the three-port valve that either sends the water from the filter directly to the heater or sends it first to the solar panels and then the heater. A check valve is installed on the pipe that returns water from the solar panel to the heater to prevent water from entering this return line when the solar panels are not in use. This might instead be another three-port valve that performs the same function as the check valve but also ensures that when not in use, the solar panels will not drain out. This might not be important where solar panels are installed at or below the water level of the equipment and pool, but most installations of panels are on rooftops, high above the water level.

A solar heating package from your pool supply house includes panels, plumbing, controls, and instructions. You should hire a licensed carpenter, to help with the installation and support of the panels and also complete the plumbing into the system.

The existing pump will probably be adequate for circulation when adding solar equipment, because the gravity and siphon effect balances the additional pressure the pump experiences trying to push the water up to the panels. Therefore, the height of the panels above the water has no effect on the pump’s ability to perform.

However you have to calculate the effect of the length of pipe and fittings as with any plumbing installation. When planning an installation, the pipes to and from the panels should be insulated so heat is not lost along the way.

Maintenance and Repair

Once installed, the solar heating system should be checked for leaks. Leaks can easily occur because of the extremes of hot and cold temperatures that cause the panel materials to expand and contract. Leak repair depends on the type of material in the panel or plumbing, and each manufacturer makes leak repair kits with instructions. The plumbing to and from the panels can be repaired as needed using the techniques outlined in the chapter on basic plumbing.

Dirt prevents the panels from absorbing heat and can cut efficiency by as much as 50 percent. Cleaning will solve the problem.

Panels can become clogged with scale from hard pool water and chemicals. Poor circulation can result due to clogging and disassembling the panels from each end and exposing the pipes of the panel that actually carry the water, and reaming these out with special brushes is the solution to it. Again, how you make this repair depends on the maker of the panel and its style. The maker should provide instructions and special tools for this procedure. As with leak repair or cleaning of solar panels, reaming is simple to perform using the right techniques and skills.

Water Level Controls

The most simple and common method of replacing evaporated water in the pool or spa is to turn on the hose. But this can take from few minutes to long hours. This can make you to forget to turn off the hose some time. To overcome this automated water fill systems are available to do this job.

There are basically two kinds of automated water fill systems and other systems with variations on those themes are available. If the pool or spa was built with a water fill line plumbed in place, the on/off anti-siphon valve can be replaced with a mechanically timed valve. In this way, you can set the water to run 1 to 60 minutes.

Instructions for removing the manual valve and installing this timer valve are in the package with the valve and are simple to follow. For this you must turn off the household main water supply. This is probably the only pool or spa repair requiring shut off of the household water supply.

First, locate the supply meter, usually in front of or alongside the house, in the ground, mounted in a concrete box. Inside the box you will see the meter with a gate valve on the outflow side of the meter. Turn this off. If it is stuck or rusted, there is a shutoff valve on the inflow side of the meter, but not with a standard handle. This valve can be turned off with a channel lock pliers or a small pipe wrench by gripping the post of the valve and turning it so it lines up across the pipe.

A variation on the timer valve is a similar unit calibrated by gallons rather than time. It screws onto a hose bib, the hose is screwed onto the timer unit, the hose bib is turned on, and the dial is set for the number of gallons you need. You determine the gallons needed by calculating how many inches of water are needed, and how many gallons are in those inches.

There are, however, some models available in gardening supply shops that include solid-state components for regularly scheduled timed water flow or preset volume flow. These require batteries and careful setting and work well if you carefully check and recheck your settings and change the batteries frequently so the system doesn’t fail.

The other type of water level control works much like the float valve in your toilet. A float which opens and closes a valve attached to a water supply line, is located at the water level desired. When the level drops, the float drops, opening the valve. As the level rises, the opposite happens. The float and plumbing can be located in the skimmer, but is more often located in a small separate reservoir tank, perhaps not even near the pool. The tank must be set at the same level as the pool, so the water in it imitates the water level of the pool. A pipe connects this tank with the pool so the actual water and its level are the same in each. Also, as the level drops, the water fills the pool through this common pipe.

These units are reliable and can be adjusted for water level by bending the arm on the float to the desired level or by setting the elbow in the float arm accordingly. A set screw loosens the elbow to allow adjustment. The small valve is threaded, so if it rusts, clogs, or fails, it can be unscrewed and easily replaced.

Water level controls serve another valuable purpose. As water evaporates, scale of minerals especially calcium are formed on the tiles and artificial rocks. So the simplest method is to keep a constant water level in the pool. As water evaporates and leaves scale, fresh water is introduced to refill the pool to cover the scale line.