Plumbing an inground pool is fairly simple stuff, but it's not hard to mess it up - if you do not have a plan and proceed carefully. The last thing you want is to have a leak underground because of a bad glue joint, or a fitting left unglued.
Most of our DIY inground pool kit customers do their own plumbing, or will have a worker do it for them; there's no need to hire a professional plumber. Before we get into some detail about how to plumb an inground pool, let's define the what, where and when.
Pool plumbing are pipes that are buried underground, connecting the pool with the filter equipment. The suction lines, skimmer and main drain, are two pipes that connect into the pool pump, via a 3-way valve. The return line is the pipe that carries water from the pool filter, back to the wall return inlets. Other plumbing lines may be connected to step jets, a pool cleaner line, or fountains and water features. Pool plumbing is done after the pool walls are erected, about halfway through the process.
The conduit or pipe that carries the power to the underwater pool light is also a part of pool plumbing, so we'll touch on that as well. And the plumbing that you do on the equipment pad, connecting pump, filter, heater, chlorinator is another important part of pool plumbing that we'll cover below.
How to Plumb an Inground Pool
- Supplies and Materials list
Take some measurements, first of all - from your equipment pad to the skimmer, main drain, returns and any other plumbing lines. Your suction pipes (skimmer, main drain) typically will come up on one side of the equipment pad, and the return pipes come out of the ground on the other side of the pad. If you haven't erected your pool walls at this point, make your best guess on the location, but before you begin to plumb, measure again, to be sure you do not run short on pipes or fittings.
Our Pool Kits Include:
- 100' - 1.5" Sch 40 Flex pipe
- 4 - 1.5" Tee fittings
- 5 - 1.5" 90 fittings
- 4- 1.5" Couplings
- 4 - 1.5" Male adapters
- 4 - 1.5" Street elbow
- 2 - 1.5" 3-way valves
- 2 - 1.5" Unions
- 1 Qt Ultra Grip Blue
- 1 Qt Purple Primer
Teflon Tape Our Pool Kits come with all you need to install an inground pool, but if your pad is located far from the pool, or if you add a cleaner or fountain line, or additional steps jets, or a slide water line - you'll need more pipe, fittings and valves.
When you measure your plumbing runs, do not forget to add the vertical amount of pipe needed, and the pipe, fittings and valves needed above ground, to connect the pool plumbing to the pool equipment.
Other supplies that you'll need include a measuring tape, a power saw, either reciprocating or jig saw, with a few sharp blades. Emory cloth or sandpaper can be used to smooth off the burrs after cutting the pipe. Teflon tape and silicone is used for threaded fittings. I like to have a rag on hand, to quickly wipe up any glue that may ooze out, and run down the pipe - keeps it looking neater.
Differences in Sch 20, Sch 40 and Sch 80
This refers to the thickness of the pipe wall. Sch stands for Schedule. A pipe labeled Schedule 20 will have a thickness of 0.100", and a Sch 40 pipe will have a 0.150" wall thickness. Schedule 80 pipe is a gray PVC, with a 0.200 wall. Sch 80 fittings can be used on pumps and filters, if you encounter a problem with Sch 40 fittings melting and shrinking, and leaking. Sch 20 pipe should not be used on pool plumbing, or pressurized lines.
6 commonly used PVC fittings
- Coupling - Used for joining two sections of pipe.
- 90 - An elbow fitting, makes the pipe turn 90 degrees.
- 45 - A half-elbow, makes the pipe turn 45 degrees.
- MTA - Male threaded adapter, Male threads x Slip
- FTA - Female threaded adapter, Female threads x Slip
- Tee - 3-way fitting, 1 pipe coming in, two going out.
Plumbing Your Pool Pipes
This stage is done after the walls are erected, the concrete collar is poured and the skimmer and returns are mounted on the wall.
When you had your pool excavated, your excavator used the backhoe, and dug a trench (or two), for the pool pipes to run underground, from the pool to the equipment pad. The trench doesn't need to be the same depth as the wall height, but are usually dug about two feet deep. Areas that get more than 3 weeks of consecutive days below freezing should dig their trenches (and lay their pipe) accordingly deeper.
First step is to level out the trench, chances are you had some cave-ins, or areas that aren't a consistent depth. Work it with shovels and picks, until you get it deep and wide enough.
Returns: Next step is to connect a MTA or threaded 90 into the back of the return fitting, And connect a piece of Rigid Sch40 PVC pipe, to the ground level, where you glue on a 90 or a 45 fitting. Now cut another 3-4' piece of rigid Sch40 pipe and glue on a 90 degree fitting - this is the piece of pipe that will stick up out of the ground at the equipment pad. Now run a continuous run (if possible) of Sch40 flex pipe, from the wall fitting pipe to the return pipe at the equipment pad.
Main Drains: This step is done before your pool hopper bottom is poured. Connect your two main drain pots together, by running a section of rigid Sch40 pipe from each drain into a Tee fitting. A rigid piece of pipe exits the Tee and connects to a 90 or 45 fitting. Connect flex pipe to this fitting, and run across the hopper pad, up the deep end side wall, and exit the pool under the wall. Then run the pipe into the trench and take it back to the equipment pad. Bring it up out of the ground, on the opposite side of the pad, so you have suction pipes on one side, and return pipes on the other.
Skimmers: Affix the skimmer to the wall of the pool with the screws provided (do not forget the gasket). Make sure to tighten it very tightly. Now, just as you had done for the return, connect an MTA into the bottom of the skimmer, and into a piece of rigid Sch40 PVC pipe that runs to the ground level and glues into a 90 fitting. Cut a 3-4' piece of pipe and glue on a 90 fitting, and stand it up next to the equipment pad, about a foot from the main drain pipe, and 2-3 feet from your return pipe. Now run a continuous run of flex pipe underground, horizontally, connecting to your two rigid Sch40 vertical pipes.
Other: If you are running a dedicated cleaner line, or a line for a fountain, or additional pool returns, the process is similar to that described above. Make sure that all of your threaded fittings seal up tight by smearing silicone into the threads and then wrapping 3-4x with Teflon tape, in a clockwise direction.
Plumbing Your Pool Light Conduit
For the conduit that is used to carry power wires to the pool light, you'll need a quantity of 3/4" gray conduit, which you can buy in 10' lengths. They have couplings built into the ends, but you may need to buy a few 90 or 45 fittings. Conduit can be heated up and bent gently with a small blow torch, to go around gentle turns.
Your conduit will need to be run from the pool junction box to the pool light niche, which mounts on the wall of the pool. The junction box may be located at the equipment pad, if that is close to the pool light, or a j-box can be mounted closer to the pool light, to meet the 50' pool light cord. The j-box can't be closer than 10 feet from the pool, and must be 18" above the water level in the pool, as shown in this image.
Run your conduit from the pool light niche, to the junction box, which is where the pool light cord meets the power cord from the breaker box, which also needs to be encapsulated in electrical conduit, rigid or flexible.
Plumbing your Equipment Pad
We've done several blog posts on this topic, listed at the bottom of this page, but here's the main points:
- Space out your equipment for airflow and serviceability.
- All pipes coming out of the ground should have the same height.
- Use as few 90's as possible, to reduce resistance.
- Allow some room for future expansion.
- You can run a pipe for future use, capped off at the pad.
- Route your plumbing away from your electrical panel.
Professional pool plumbers always pressure test their plumbing when complete, to be sure that their work was solid, no matter what may happen after they leave the job site. You can also pressure test your pipes and glue joints by using a Drain King and pipe caps or plugs. Use the drain king to pressurize a pipe with a very tight plug or glued cap on the other end. Inspect the pipe and fittings while under pressure for any drips.
Backfill the Trenches
I like to wait to backfill the trenches until we have the pool pump and filter operating; that's my method of pressure testing. The liner goes in and the pool is filled. Then we install the faceplates and flood the lines. Let the system run for a day, and if you do not see any wet spots on dry soil, then we're ready to backfill around the pool, and in the pipe trenches. Fill and compact the soil gently so that you do not put pressure on underground pipes and fittings.
Tips for making a good glue joint
- Make straight cuts across the pipe.
- Remove rough edges or burrs on pipe.
- Use primer just before glue - on pipe and fitting.
- Use liberal amount of Fresh glue, on pipe and fitting.
- Use only deep socket, pressure fittings - Sch 40
- Push together and hold firm for 20 seconds after gluing.
When you reach the stage of plumbing your inground pool, the SPP Pool Experts are right there with you - ready for any questions or concerns, or just to review the plan, and the supplies on hand.
SPP Pool Expert
- How to Build a Pool: Inground Pool Kit Plumbing
- Plumbing for Your Inground Pool Kit
- How to Build a Pool: Installing the Underwater Light