How Does Fiberglass Pool Plumbing Work?

I well remember well my first pool experience. The home we purchased had a large pool installed, and there was a shed in the back which housed all the equipment. Because we were not the original buyers, there was no orientation, no instruction, no labels and a really complex looking series of valves. I had no idea.

Every pool is the same when it comes to the basic fluid hydrodynamics, which is a fancy term for what happens to the water. If you have never owned a swiming pool before, however, this might as well be Quantum Physics, and we all are worried about turning the wrong thing and doing damage. Here in its simplest form is what happens when you pump starts.


  1.  The pump electric motor begins to spin, turning the impeller, which is the part of the pump that forces water through the pipes.

  2.  As the impeller turns and forces water through the pipes (referred to as the pressure side of the pump), it draws water in through the front of the pump (referred to as the suction side) which comes from the pool. The suction side water will come from the main drains, the skimmers, or usually, a combination of both. The key point to understand, is that all this activity is contained within a loop – the same water goes around and around – it just needs to be cleaned.

  3.  As the water is drawn into the front of the pump, large debris, such as leaves, will be caught in the strainer. The strainer is what you see when you look down through the clear plastic top of the pump. Water, (but not large debris) passes through the strainer, and immediately is drawn through the impeller and forced into the filter.The pump electric motor begins to spin, turning the impeller, which is the part of the pump that forces water through the pipes.

  4.  As water moves through the filter, it is cleaned, oils and small debris are removed, and the water, now cleaned is forced back into the pool through the fittings on the wall known as the returns. A good pool pump will typically move 5000 gallons of your pool water every hour. There are a lot of different things that can be applicable in this sort of calculation, # of valves, # of 90 degree fittings, size of the pipe, length of the pipe, type of pipe – they make my head hurt. For now, just understand that the more often your water goes through the filter the cleaner it will be.

  5.  As things begin to collect in the filter, it becomes more difficult for the pump to swimming pool filter pressure gaugepush water through the filter. That pressure is reflected in the pressure gauge. The higher the pressure, the more the need to clean the filter. The general rule is that when the pressure rises to 10psi above normal operating pressure – time to clean.


This is the simple form of the plumbing in your swimming pool. There are a lot of other things that can be described here, but everything that happens in your pool happens in that cycle somehow. If you add a heater, the water goes through the heater, is heated up, and goes to the pool. If you add a water feature, the water is directed through the waterfall or fountain, and goes back to the pool. As you think about what is happening in your pool, remember there is nothing magical happening. The water is drawn from the pool, cleaned and sent back to the pool. Sometimes it is send back through various features, or pool cleaners, or along decorative waterways, but it will always be water in a circle.

As a homeowner, the important things for you to know are that you should expect your builder to use 2″, “Schedule 40″ PVC pipe for your pool – not 1 1/2” PVC. Bigger pipe means better water flow, which means your water gets cleaner faster. Also a bigger pump is not always better – the pump and filter should be sized to the pool, because too much pressure on your lines can cause serious damage over the life of the pool.

Swimming pool plumbing will appear to be very daunting the first time you look at it, but a year after the pool is finished, and you have had a summer full of poolside fun, the whole thing will be as child’s play – and that is exactly what it should be. Swimming pools bring out the kid in us all, and worrying about plumbing should be left to your builder.

Have Fun!



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