In a Summerville summer — July highs around 91°F, blazing sun, afternoon breezes — every pool loses water to the air. The question is whether your pool is losing a normal amount or a leak amount. The bucket test answers it definitively, costs nothing, and takes a day. Here's how to run it right.
How much evaporation is normal
Evaporation isn't a fixed number; it rises with heat, sun exposure, wind, and low humidity, and falls on cool, still, overcast days. A pool in full Lowcountry sun during a hot, breezy week can lose noticeably more than the same pool in a mild spring week. That's why comparing against a control — the bucket — beats guessing against a rule of thumb.
The bucket test, step by step
Fill a bucket about three-quarters full with pool water and set it on a pool step so the water inside and outside the bucket start at roughly the same temperature. Mark the water level inside the bucket and the pool's level on the outside of the bucket or the skimmer. Run the pump on its normal schedule for 24 hours, keeping swimmers and splash play out of the pool. Then compare the two marks.
Reading the results
Both levels will have dropped — that's evaporation, and the bucket shows exactly how much the weather took. If the pool dropped by the same amount as the bucket, you're looking at evaporation, not a leak. If the pool dropped clearly more than the bucket, water is leaving through something other than the air: that's a leak.
Signs pointing to a real leak
Even before the test, certain clues argue for a leak over evaporation: the water level falling faster when the pump runs versus when it's off, air bubbles in the pump basket or return lines, soggy spots or unusually lush grass near the equipment pad, cracks in the deck or skimmer, and a pool that needs refilling far more often than in past summers.
Where pool leaks hide
Most leaks live at penetrations and joints, not in the middle of the shell. Prime suspects include the skimmer throat and its seal to the pool wall, return fittings, the light niche and its conduit, main drain covers, and the plumbing runs between the pool and the equipment pad — especially at elbows and valves. Vinyl liners add tears and separated seams to the list; concrete pools add structural cracks.
The pump-on vs. pump-off test
This narrows the search before any equipment arrives. Mark the level with the pump running normally for a day, then with the pump off for a day (keep the bucket test running for both). Faster loss with the pump on points to the pressurized plumbing — returns, equipment, underground lines. Faster loss with it off points to the shell itself — skimmer, liner, light niche, main drain.
Is the spa losing water too?
Attached spas share plumbing with the pool, and a spa that drains down to pool level overnight is a classic check-valve or shared-line issue rather than a shell leak. Note whether the spa holds its level independently — that single observation tells a technician a great deal about where to look.
Common pool-leak myths
Dye tests from a bottle find only the most obvious skimmer leaks; most leaks won't show. Leak-seal additives rarely fix structural or plumbing failures and can gum up filters. And "all pools leak a little" is only true in the evaporation sense — a pool that needs the hose weekly in a mild month has a problem worth finding.
The equipment pad: an overlooked leak zone
Many pool leaks aren't in the pool at all — they're at the equipment pad. Filter housings, pump seals, heater connections, and the maze of valves and unions can weep steadily, with the water evaporating off hot concrete before anyone notices a puddle. During the pump-on test, walk the pad slowly and look for damp fittings, mineral crust on joints, and the sound of hissing at connections. A surprising share of "pool leaks" turn out to be a five-minute fitting fix at the pad rather than anything underground.
When to call for professional detection
Call when the bucket test confirms a real loss, when the pump-on/off test points to plumbing, or when visible suspects check out but the water keeps dropping. Professional pool leak detection pressure-tests the plumbing lines individually and pinpoints the failure — so the fix opens one fitting, not the whole deck. Call +1 843-936-8115 — open 24 hours.