Port St. Lucie Leak Detection Losing water only when the pump runs (or only when it is off)
This is the single most useful diagnostic observation in pool leak work, and it costs nothing to make. Watch the pool with the pump running and with it off, and note whether the loss rate changes.
What the answer tells you
| Pattern | Which side | What it usually is |
|---|---|---|
| Loses water only when the pump runs | Pressure side | Return lines or a return fitting, under pressure and pushing water out |
| Loses water only when the pump is off | Suction side | Skimmer or main drain line, draining back through a break |
| Loses at the same rate either way | Static | The shell, the skimmer, the light niche, or a fitting |
| Loses much faster when the pump runs | Pressure side | A significant return-line break |
| Air bubbles at the returns, pump loses prime | Suction side | Air being drawn in at the break |
That table is why the question is worth answering on any call. It halves the search before anyone arrives.
How to run the test properly
- Mark the water level precisely on the tile with tape.
- Run the pump for 12 hours on its normal schedule, then mark again and measure the drop.
- Leave the pump off for 12 hours, mark again, and measure.
- Compare. Same drop in both periods means a static leak. More with the pump on means pressure side. More with the pump off means suction side.
- Do a bucket test alongside it to rule out evaporation, which in a Treasure Coast summer is a real number. The bucket test post has the method.
Top the pool up to the same starting mark before each period so you are comparing like with like.
Other clues worth noting
Air in the system. Bubbles coming out of the returns, a pump that loses prime, or a pump basket that will not stay full all point at the suction side. A suction-side break lets air in as well as water out.
A wet spot in the yard or a soggy deck section. That is where the water is going, and it is a strong pointer. Note whether it is worse when the pump runs.
Sinking or lifting pavers, or a deck section that has moved. Water washing out the sand base under a deck does that, and on the sandy soils here it happens faster than people expect.
A pressure gauge reading lower than it used to at the filter, on a system that has not otherwise changed.
What the repair actually costs, and why
$500–$1,500 and up. The pipe itself is inexpensive. What decides the number is what is on top of it:
| What covers the line | Impact |
|---|---|
| Open ground or planting bed | The cheap case, dig and repair |
| Pavers | Lift, repair, relay. Usually straightforward |
| Poured concrete deck | Cut, repair, and patch. Patching never matches perfectly, and you should hear that first |
| Under a screen enclosure footing | The expensive case, access work before any plumbing |
| Under the pool shell itself | Rare, and a different conversation entirely |
There is also a genuine alternative worth asking about: rerouting. Where a line can be abandoned and replaced on a different path, around the deck rather than through it, the deck stays intact. It is not always possible and it is not always cheaper, but it should be on the table before anyone starts cutting concrete.
The pool plumbing leak repair page covers the work and the pricing page publishes every range.
Why pressure testing matters
A plumbing leak cannot be found by looking. The detection visit pressure tests each line individually: isolate the line, put it under pressure, and watch whether it holds. A line that will not hold pressure is the leaking line, and from there electronic location narrows it to a point rather than a guess.
That is the difference between cutting one three-foot section of deck and cutting a trench across the whole thing.
The visit is a flat $250–$400 for a standard residential pool, $350–$500 with a spa, and $400–$550 with spa and water features, and it produces a written report plus a separate repair quote. The cost calculator prices both halves.
What to expect on the call
Your two measured drop rates, pump on and pump off. Whether there is air in the system. Whether there is a wet spot, and where. Whether any deck or pavers have moved. That is most of the diagnosis before anybody drives out. We cover Port St. Lucie, Fort Pierce, Jensen Beach, Stuart, Palm City, Port Salerno, and St. Lucie West.
Frequently Asked Questions
My pool only loses water when the pump is running. What does that mean?
The leak is on the pressure side: the return lines carrying water back to the pool, or a return fitting. When the pump runs, those lines are under pressure and push water out through the break. When it stops, the pressure drops and so does the leak.
What if it only loses water when the pump is off?
That points at the suction side: the skimmer and main drain lines. Those lines sit under static head when the pump is off and can drain the pool back through a break. When the pump runs, the suction actually pulls water in rather than pushing it out, so the leak appears to stop.
What does underground plumbing repair cost?
$500–$1,500 and up. The variable is not the pipe, it is what is on top of it: pavers lift and relay cheaply, a poured concrete deck has to be cut and patched, and a break under a screen enclosure footing is the expensive case. The number is firm only after the break is pinpointed.
Can a plumbing leak be fixed without digging up the deck?
Sometimes. Where a line can be rerouted or abandoned and replaced on a different path, the deck stays intact. Where the break is at a fitting under the deck, it usually cannot. The pressure test shows which you have; be wary of anyone promising a no-dig repair before it is done.