When a pool loses more water with the pump on, the leak is on the pressure side, the return lines that carry water underground from the equipment back to the pool. Here is how to read this clue and what it means.
Call (954) 290-5177, Free Estimate →When a pool loses more water with the pump running than with it off, the leak is almost certainly on the pressure side of the plumbing, the underground return lines that carry water from the pump and filter back to the pool under pressure. Any crack or fitting failure on those lines leaks at a higher rate under pump pressure. Knowing whether the pool loses more water pump-on or pump-off is one of the most useful diagnostic clues before the detection visit.
Pressure-side leak. The underground return lines (from pump to pool returns) are pressurized when the pump runs. Any failure on those lines leaks at a higher rate under pump pressure. This points to the return plumbing, valves, or fittings after the pump and filter.
Static leak. A failure in the pool shell, skimmer, light niche, or suction-side plumbing that leaks under water weight (hydrostatic pressure) regardless of pump status. The pump is not the variable.
Less common, can indicate suction-side issues or a static shell/skimmer leak where pump draw is actually slightly reducing the rate. Discuss this pattern when you call.
Strong indicator of a pressure-side underground failure. When the pump stops and the lines depressurize, the leak slows to essentially nothing. This is a clear sign of a return line failure.
Before the detection visit, we ask every homeowner this question: does the pool seem to lose more water when the pump is running, when it is off, or about the same either way? The answer narrows our focus before we arrive. A pump-on pattern means pipe testing of the return circuits is a priority. A pump-off or constant-loss pattern points toward the shell, skimmer, and light niche as the first area to test.
Use the free Leak Analyzer and Free Guide from Leak Business Academy to score what you are observing.
Leak Analyzer → Free Beginner Guide →When a homeowner tells me the pool drops fast when the pump is on and barely drops when the pump is off, I already know I am looking at a pressure-side pipe failure before I pull up to the house. That observation, combined with the water level pattern, tells me which circuits to pipe test first. I am not starting from zero when I arrive.
Tell us what you have noticed about pump-on versus pump-off loss when you call. The more specific you can be, the faster we can confirm the source.
Leak and Subsurface Locators finds pressure-side and shell leaks throughout South Florida. Licensed CPC1457277. Free estimate before scheduling.
(954) 290-5177 (561) 325-2678 (561) 325-2678Yes. A visible drip at a pump fitting, filter housing, or heater connection is also a pressure-side leak, just above ground instead of underground. Check the equipment pad while the pump is running for any wet fittings, dripping connections, or wet areas in the surrounding soil. If you see it there, that is useful information before the visit.
We cap the pool returns and pipe test each return circuit individually. We introduce air or water pressure into the circuit and observe whether pressure holds or bleeds off. A circuit that will not hold pressure has a failure somewhere along that run. Trace gas or acoustic equipment then locates the failure underground before any cutting begins.
Not necessarily. A shell or skimmer leak loses water regardless of pump status. If the loss is significantly higher with the pump on, there may be both a static leak and a pressure-side leak. We test both during the visit and document every confirmed source.