Plumbing Fittings Used On Swimming Pools

Common Plumbing Fittings Used For Installing Pool Equipment

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When you are installing a pump, filter, heater or any peripheral items like chlorinators or salt water systems you will likely need to make changes to your existing plumbing system. There are many different components that are needed and the information on this page will help you to determine what you have currently and what you will need to purchase in order to adapt your new equipment.

The first order of business is to determine what you have currently in terms of pipe material and size so that you can get the correct fittings for your system. The two common style of fittings that you will need are schedule 40 PVC (primer and glue) and barbed poly fittings (interior fit & clamped). Most pool systems should be upgraded to glued PVC, especially above grade where you can easily access the pipes. If you are doing extensive work on your equipment pad and you have poly style piping, then you should consider stripping out the old poly and re-plumbing the entire system with PVC pipe and fittings.

Pipe Sizing For Swimming Pool Equipment

Almost all residential swimming pools are plumbed with either 1.5" or 2" pipe. Older pools especially are almost all 1.5" pipe where newer pools tend to incorporate 2" plumbing more often as this allows for a substantial increase in efficiency of your plumbing system. As a quick reference, 2" pipe is about the diameter of a can of soda, where 1.5" pipe is somewhat a smaller diameter than a standard sized can. The fittings that you have, as well as the pipe, will often have the pipe size printed right on them if you are still not sure what you have.

Should I upgrade the pipe to a larger diameter? - It is not uncommon to have the equipment pad plumbed in with 2" pipe as a method to improve the flow of the system. The friction loss of a plumbing system goes down dramatically as you increase the pipe diameter size which means that upgrading your equipment pad to 2" pipe will noticeably improve the flow of your system. It should be noted that the ability to do this will depend on the size and number of suction lines you have in the pool. A single 1.5" suction line coming to the pump will not provide enough flow to justify upgrading the pad to 2" pipe. If you have 2" suction lines, or multiple 1.5" suction lines then you should consider upgrading everything on the pad to 2" pipe - but most specifically the pipe on the suction side of the filter. If you upgrade the suction line manifold in front of the pump to 2" and the pipe from the pump to the filter to 2" then you will make life easier on your pump and improve the flow dynamics of your system.

How To Improve Flow Dynamics Of Pool Equipment

There are a few things that you should avoid doing to make sure you get the maximum flow, and maximum life, out of your swimming pool circulation system. In a closed loop plumbing system the total amount of resistance to flow is called head pressure. The more fittings that you use, the more increase in the resistance to flow, which means that your pump will need to work harder to move water through the system. This will result in greater heat generation from your pump and a reduction in the potential flow of the system. The heat can damage the pump and shorten the expected service life you will get from it, and the decrease in flow will negatively affect the circulation and filtration of your pool water.

Choose your pipe fittings carefully - Every fitting you use adds to the resistance to flow. A sharp bend 90 degree elbow fitting (like a street elbow) has a pronounced increased in resistance to flow where a gradual sweep elbow will result in less resistance to flow. If you can fit a sweep elbow in place, then why would you ever want to use a street elbow? Seems simple, but if you have watched any of my equipment installation review videos then you will see that street elbows are everywhere on pool equipment. Learn from these videos and make sure that your system is free of street elbow fittings.

Use the fewest fittings possible - Back to back fittings, or multiple fittings within a short run of pipe is a major flow restriction. There are a lot of factors at work that all contribute to the total dynamic head of a plumbing system such as diameter of pipe, length of run, number of fittings / restrictions and smoothness of the pipe. As part of this, the turbulence of the water has a great deal to do with the resistance to flow experienced from friction loss as water passes through a fitting like an elbow. The water becomes turbulent as it passes through a flow restriction which increases the friction loss. If the water is still turbulent from being forced through a street elbow and immediately has to be forced through another restriction like another elbow, the friction losses due to the turbulence in the water multiply. In short, use as few fittings as possible, choose low resistance fittings like sweep elbows over street elbows, and space your fittings as far away from each other as possible.

Standard Plumbing Terms For Pipe Fittings

MPT (MIPT) = Male pipe thread (male iron pipe thread)

FPT (FIPT) = Female pipe thread (female iron pipe thread)

Slip (socket) = The receiving end that you glue pipe into

Spigot = The pipe size made to fit inside a slip

Street elbow = Tight radius bend 90 degree fitting

Sweep elbow = Gradual radius 90 degree fitting

Barbed fitting = Fitting made for interior fit / clamp system

Bushing (reducer bushing) = Fitting made to transition from one pipe size to another

Schedule 40 PVC Pipe Fittings

Part number 406-015 - This is a standard slip by slip elbow fitting and is one of the most commonly used fittings for swimming pool equipment installation. This is the preferred elbow fitting over a street elbow (part number 409) as this has 4 times less restriction to flow than the street elbow. For 2" pipe use 406-020 - 2" PVC Elbow





Part number 436-015 - This is a male adapter (slip x MPT) for threading into female threads like found on most pool pumps and filters. Most swimming pool equipment installations will require at least a few of these fittings. For 2" pipe use 436-020 - 2" PVC Male Adapter




Part number 435-015 - This less commonly used fitting is female (FPT) x slip and is the reverse of the 436 male adapter. You would typically only need this fitting in your have an existing MPT that you need to connect to. Most pool equipment is already FPT which requires a MPT to connect to it. For 2" pipe size use 435-020 - 2" PVC Female Adapter




Part number 417-015 - This is a slip by slip 45 degree elbow fitting. Using two of these in place of a 90 degree elbow reduces the resistance to flow by approximately 10%. They are also useful for making an offset in the plumbing without using two 90 degree elbows which would restrict the flow much greater than two 45 degree elbow fittings. For 2" pipe use 417-020 - 2" PVC 45 Degree Elbow




Part number 429-015 - This is a slip x slip coupling which is used to connect two straight pieces of pipe together. Any time that you are cutting into a pool system to make changes you will almost certainly need a few of these couplings. For 2" pipe use 429-020 - 2" PVC Coupling




Part number 401-015 - This is a standard slip x slip x slip Tee fitting. Use these fittings for consolidating multiple lines into one as when installing pump suction manifolds or return manifolds. Also used for zoning in peripheral equipment if you are creating zoned bypasses for any items that you are installing. For 2" pipe use 401-020 - 2" PVC Tee




Part number 409-015 - The dreaded street elbow...This fitting is slip by spigot so you can glue pipe into one side and the other side directly into another slip fitting. This makes for very tight connections which can be useful in a manifold where the pipes are too close together to fit 406 elbows. Wherever possible these 409 street elbows should be replaced with 406 elbow fittings to improve flow dynamics of your plumbing system. For 2" pipe use 409-020 2" PVC Street Elbow

Transitioning Between Pipe Sizes & Materials

If you are going to encounter any kind of problem installing your pool equipment it might likely be in the transitioning from one style of pipe to another, or changing the pipe diameter. Not that these are hard to do, but if you are mid-way in your equipment installation and realize that you are missing one of these fittings then you will not be able to complete the job.

Part number 437-251 - This is a slip by spigot reducer bushing for reducing from 2" down to 1.5". The spigot on this reducer would glue into a 2" slip and then you glue the 1.5" pipe into the slip on this reducer.




Part number P1056-015 - This is a Fernco coupling which is a suitable method to transition from ABS to PVC where applicable. Fernco fittings are also sometimes used to create a rubber buffer at various points in the plumbing system in order to reduce vibration and noise from the pipes. For 2" pipe use 1056-22 - Fernco 2" Coupling




Part number P1056-215 - This is a Fernco reducing coupling for transitioning from 2" to 1.5" pipe. This is useful for if you need to transition both pipe size as well as pipe material in a single fitting.




Part number 474-015 - This is an adapter to go from existing poly pipe to PVC pipe. The barbed end of the fitting is inserted into the poly pipe and clamped with 2 stainless steel hose clamps. The other side of this fitting is a PVC slip connection that you can glue 1.5" pipe directly into. For 2" pipe use 474-020 - 2" PVC Barb x Slip Adapter

Poly Pipe Barbed Fittings

While antiquated, there are still many swimming pool plumbing systems in operation that are plumbed with poly pipe. While there are a few different kinds of poly pipe, they all share the similarity that they use interior fit barbed fittings along with stainless steel hose clamps instead of solvent welding like with the PVC. It is much harder to get a leak free seal with barbed fittings and clamps as opposed to with glued PVC pipes but still easy enough that anyone can do it with a little care.

Heat the poly pipe - An installers tip is to use a torch or a heat gun to heat (not burn) the poly pipe right before you tighten the hose clamps. This will allow for a much tighter and leak free fit with the barbed fitting

Use a ratchet or wrench - Instead of using a standard (slot) screwdriver to tighten the hose clamps, you may find that a 5/16" socket and ratchet, or a small wrench, will help to get the clamp tight enough for a leak free result. You do not need to tighten as much as you can with the wrench or socket but likely more than you will be able to tighten with a screwdriver or nut driver.

Part number 1406-015 - This is a 1.5" barbed 90 degree elbow fitting for use with poly style pipe. The barbed end is inserted into the pipe and hose clamps create a leak free seal. For 2" pipe use 1406-020 - 2" Barbed 90 Degree Elbow




Part number 1429-015 - This is a barb x barb coupling for connecting straight pieces of poly style pipe. For 2" pipe use 1429-020 - 2" Barbed Coupling

You may learn a few things about plumbing pool equipment by watching my video series on Pool Equipment Installation Reviews.


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Swimming Pool Steve is an award winning, second generation swimming pool and spa specialist from Ontario Canada. With over 10,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the 2018 Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.


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