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    How to Build a Pool: Inground Pool Kit Plumbing

    February 5, 2013

    Pool Plumbing Unions and Valves

    Our inground pool kits come with a starter plumbing kit. We give you valves, unions, assorted schedule 40 PVC fittings and 100 ft of schedule 40 flex pipe. In some cases you will need additional pipe, depending on the size of the pool, how many returns and skimmers, and any other water features you are planning, and the distance to the pool equipment. Extra pipe can be ordered at the time of the pool kit purchase and delivered along with the kit, or you can get extra pipe locally, either flex or rigid PVC.

    Flex or Rigid PVC Pipe?

    Flex pipe is much easier to work with; it lays flat in the trenches and makes turns without using flow restricting fittings. It also compacts in the soil more fully, and is less likely to break under compaction. Rigid PVC pipe is stronger against chemical degradation and resists problems from earwigs in the soil.

    Many of our customers use rigid PVC where the pipe comes up out of the ground, and use flex pipe for the underground plumbing. Connecting the equipment with rigid PVC above the ground, looks neater, and makes the equipment less likely to move.

    1.5" or 2" PVC Plumbing?

    plumb-poolIf you are upgrading to a Variable speed pump and filter with 2” ports, it is a good idea to increase the pipe size to 2” instead of the standard 1 ½" pipe. Variable speed pumps need 2 inch pipe to give a better flow and most cost savings - which is why you are purchasing the variable speed pump. Large water features, or powerful spa jets are another area where 2" pipe may be used.

    Pool Plumbing Trench

    When your pool is being dug, have the operator dig a trench from the pool to where your pool equipment will be (your equipment pad). This will save you from hand digging a pool plumbing trench after the machine leaves your yard. Make sure it is at least about 2 ft wide and at least 2 ft deep. This will ensure enough room to fit all your pool plumbing lines and electrical conduit also.

    How Deep Should Pool Plumbing Pipes be Buried?

    Your plumbing lines should be about 2 ft underground to protect them from surface soil slip and shift and from freezing temperatures. If your pool is in the southern U.S., with rare freezing temperatures, you can bury your pool pipes a bit shallower, but if you can go deeper, it's always a good idea. And, do not forget to call your local Dig Safe service, to have your utility lines marked (for free), before beginning any digging in your backyard.

    If you're  in a cold weather climate, you will need to winterize your lines and equipment before freezing temperatures hit. This is done by blowing the lines and equipment out with a small compressor or blower vac. After the lines are cleared of water, the returns and skimmers are plugged at the pool, to keep water from re-entering the pipes during the winter.

    How to Plumb an Inground Swimming Pool

    PVC pipe will connect the pump with the suction lines from the skimmer and main drain, and will send water back to the pool through the return lines, after the filter and any pool heater. The pipes will lay in the trench, and come up from the bottom of the trench to connect to the pool returns and skimmers on the pool side, and on the other end, the pipes connect to the pump and filter.

    Coming up out of the ground next to your pool equipment pad will be the suction lines, or the skimmer and main drain line, within a foot of each other. A few feet away, and your return pipe should come up out of the ground, also just next to the equipment pad. The pipes bringing water from the skimmers and main drain will connect into a "suction manifold", with the use of valves, and come into one pipe, which connects into the pump. On the return side, after the filter or any heater or purification equipment, the return pipe will enter into the ground. If you have separate jets or a water feature, then a "return manifold" is made with the use of valves.

    Dual Main Drains

    Main Drains: Your two main drain pots should already be in place at the bottom of the deep end at least 3 ft apart from each other. Connect the 2 main drains with your PVC flex pipe then in the middle cut the pipe and glue in a T,  from that T we will run a line all the way back  underneath the wall panels and into the trench from pool to pad and just leave it there next to the pool pump.

    Skimmer: There are 2  holes at the bottom of each skimmer, one gets plugged (usually the front hole) with the PVC plug included with the skimmer. Be sure to use Teflon tape and a little pipe dope or silicone to prevent leaking. In the other hole of the skimmer, thread in a pvc pipe connector and glue your skimmer pipe into the fitting.

    Returns: On your return inlet fittings  you can tie them in together and then come back to the filter side with one line. You can run two separate return lines, if you like. This gives you more control over the flow coming from each return but can add $100 to plumbing cost. If your pool steps have our step jet kit you will run one line from the two jets back through the trench bring it up next to the other return pipe, where it will connect into a return side valve.

    Plumbing your Inground Pool Equipment

    Pool Plumbing Diagram

    Your equipment pad is preferably a steel reinforced concrete slab, but heavy duty HVAC skids, set on a 4" gravel base can also be used. Set your pump, filter, heater, etc., on your equipment pad in a logical order, leaving lots of room for future repairs or service. Also keep in mind any codes that may exist for placement. Heaters or heat pumps have special installation requirements.

    Now that you have all your lines run from the pool to the pad it is time to start connecting to your equipment. Lets start with the pump. In the front of the pump install a PVC union (not shown), and from that connect a short piece of pipe into a 3 way Jandy valve. Unions are useful for removing the pool pump easily for service or indoor winter storage. Check valves can be used if desired; they are especially helpful if the pump and filter is located more than 12" above water level.

    Clean and glue your main drain pipe into 1 side of the valve and your skimmer to the other side of the valve. If there are two skimmers, a second 3-way valve is used, as shown in the pool plumbing diagram above. After the pump install a union, and then plumb to the inlet of your pool filter. If you have any other accessories that is where you pipe to next from the filter after putting in a union and then pipe to either a heater, heat pump, salt system or anything else then from there to a Jandy 3-way valve. In one side of the valve goes your step jets and in the other side goes your return fittings.

    Pool Plumbing Techniques


    When gluing PVC pool pipe into couplings, unions, valves or other fittings or connectors, the proper way is to clean the inside of the fitting and the outside of pipe, get it good and clean with a PVC primer. A good rule of thumb is clean it until you no longer see any writing (or dirt), so you know its clean. Within 15 seconds of cleaning, apply a liberal coating of fresh PVC glue on the inside of the fitting and the outside of the pipe. Push the pipe fully into the fitting with a small turning twist, and hold it for 30 seconds before releasing.

    Threaded fittings require extra care to prevent cracks and leakage. Use 3-4 wraps of Teflon tape, in a clockwise direction around threaded male fittings. For extra security, first spread a thin layer of silicone or pipe dope over the threads, before wrapping with Teflon tape. When tightening threaded fittings into pumps, filters, heaters, chlorinators... be careful not to over-tighten, but turn only 1-2 turns beyond hand tight.

    Pool Plumbing Tips

    • Make a plumbing diagram, measure twice - cut once, and dry fit everything together first, before gluing your pipes and fittings.
    • Use as few 90's and 45's as possible, to keep total system resistance as low as possible. Remove unnecessary turns in the plumbing.
    • Above ground pipes should be supported, and allow room to service equipment and move around without damaging pipes.
    • Leave at least 6" of clear pipe on both sides of any piece of installed equipment.
    • Plumb in order, from Pump to Filter to Heater to Chlorinator or Salt System.
    • Avoid plumbing loops where freezing water may become trapped.

    Future Piping Plans

    If you know when you install your pool that down the road you may want to add some water features, or an automatic pool cleaner, it is a good idea to run the underground piping when you install your inground pool kit. Unused pipes can just "stub-up", out of the ground and be capped off, just above ground level for fountains, or be connected through the pool wall with a wall return fitting.

    At the filter end these would tie in on the filter side or return side of the equipment,  you can just stub it up there and cap it also.  Any water features should have there own valve to turn them on and off, you could install it now on the return side of the equipment, stub  a piece of PVC out of it and glue on a cap at the end and when you do install your waterfall or whatever the water feature is you have you’ll be ready to go.

    Plumbing your own swimming pool, as you build your backyard paradise is no big deal. With the trench dug, the pipes from the pool to the equipment pad and back to the pool can be connected in just a few hours.

    If you have any questions about inground pool kit plumbing, or run into any troubles while plumbing your inground pool, give our pool plumbers a call here at Specialty Pool Products - we're here to help!  

    Larry Weinberg
    SPP Pool Expert

    Blog Author
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