Why is my pool losing water?
A pool that loses more water than a nearby bucket under the same weather conditions probably has a leak. The most useful clue is whether loss is faster with the pump running, pump off, or both.
Pump-on loss points toward pressure-side plumbing, returns, or equipment discharge. Pump-off loss can point toward suction plumbing or a leak at the resting water level. Similar loss in both states suggests the shell, liner, skimmer, light niche, or another static opening.
Pool level dropping every day?
Share when the water falls and whether the pump changes it. We review the request for one matched local pool-repair pro when coverage is available.
What the water-loss pattern can mean
Normal evaporation
No repairHow to tellThe pool and a partially filled bucket lose about the same amount under the same sun, wind, humidity, and water temperature
The fixTrack both levels for 24–48 hours with autofill off before assuming a leak
Equipment-pad leak
$100–$800+ depending on equipmentHow to tellWet soil, drips, mineral tracks, or water beneath the pump, filter, heater, valves, or waste line
The fixRepair the failed seal, fitting, valve, tank, exchanger, or discharge path
Pressure-side return leak
$300–$1,000 detection; repair separateHow to tellWater loss increases while the pump runs; soil may stay wet near a return line or equipment path
The fixIsolate and pressure-test return circuits before excavation
Skimmer, liner, light, or shell leak
$100 patch to $1,500+ structural/access workHow to tellWater falls consistently and may stop near a fitting, tear, crack, skimmer mouth, or light niche
The fixDye-test the suspected opening and repair the confirmed failure
Backwash or autofill problem
$100–$500 typical valve or control repairHow to tellWater leaves through a multiport waste line, stuck valve, overflow, or an autofill masks the true loss
The fixInspect waste discharge and disable autofill temporarily while measuring
Run these observations before the service call
- Turn off autofill, mark the pool and bucket levels, and compare them after 24 hours under the same conditions.
- Repeat the observation once with normal circulation and once with the pump off if it is safe to do so.
- Walk the equipment pad and waste line looking for drips, wet soil, mineral residue, and air in the pump basket.
- Note where the water level seems to stop. A stable level near the skimmer, return, light, or liner damage can narrow the test.
Unlock the hiring checklist
Use this before you call a pool repair, so you know what to ask and what to avoid.
Call a pro when…
- The pool drops faster than the bucket test
- Loss changes materially when the pump runs
- Water falls below the skimmer or another fitting
- The pump draws air, loses prime, or runs dry
- Deck movement, shell cracks, electrical fixtures, or buried plumbing may be involved
Repair or replace?
Most isolated pool leaks are repairable. Replace a component when the body itself is cracked, brittle, obsolete, or repeatedly leaking—for example an aging skimmer, filter tank, heater exchanger, pump housing, or liner with widespread deterioration. Pressure-test and locate buried plumbing failures before approving excavation or rerouting.
Pool level dropping every day?
Share when the water falls and whether the pump changes it. We review the request for one matched local pool-repair pro when coverage is available.
Related questions
Why does my pool lose water only when the pump is on?
That pattern often points to the pressure side: return lines, fittings, filter or heater leaks, or a waste line passing water. It is a clue, not proof; isolate the equipment and plumbing before repair.
Why does my pool lose water when the pump is off?
Pump-off loss may expose suction-side plumbing or a static opening at the skimmer, liner, shell, drain, or light. Compare pump-on and pump-off measurements over similar periods.
Will a pool leak stop at the level of the leak?
Sometimes. A leak at a skimmer, return, light niche, or liner tear may slow or stop near that elevation. Underground plumbing and hydrostatic conditions can produce less obvious patterns.
Sources and methodology
Ranges are planning estimates, not quotes. We compare published cost data with manufacturer troubleshooting guidance and separate diagnosis from repair.