Pool Leak vs Evaporation Bucket-Test Calculator

The bucket test pits your pool against a control. The bucket loses water only to evaporation; the pool loses water to evaporation and any leak. Subtracting the bucket's drop from the pool's drop isolates the leak: net loss = pool drop − bucket drop. Because the bucket sits in the same sun and wind as the pool, it's a far more reliable signal than any fixed "quarter-inch a day" rule of thumb, which is a Southern-California-climate guideline, not a hard line.

netDropIn        = poolDrop − bucketDrop          (the netting)
netDropInPerDay  = netDropIn × (24 / testHours)   (normalize any test window)

rectangular: galPerDay = length × width      × netDropInPerDay × 0.6233
round/spa:   galPerDay = diameter × diameter × netDropInPerDay × 0.48929

galPerHour   = galPerDay / 24
galPerMinute = galPerDay / 1440
cost/day     = (galPerDay / 1000) × your rate   (× 30.4 month, × 365 year)

We always apply the gallons formula to the net loss, never the raw pool drop — using the raw drop would count evaporation as a leak and overstate the loss. We also normalize to a per-day figure before judging the verdict, so a 48-hour test is correctly halved rather than read as twice the leak. The constants (0.6233 gallons per ft² per inch, rectangular; 0.48929 on diameter² for round pools and spas) assume feet and inches, so any centimeter or meter input is converted first.

Reading the verdict. The net per-day difference bands as: equal drops → no leak (normal evaporation); up to a quarter-inch → borderline (re-test to confirm); a quarter to a half-inch → possible leak; more than a half-inch → likely leak. A possible or likely result is a prompt to book a professional leak inspection, not a diagnosis — this tool doesn't assert a leak exists or locate one.

If you are the one taking that call, the next question is what the visit is worth. The leak detection pricing calculator prices the dye, pressure and listening work by the time it actually takes rather than by a flat call-out, and where the bucket result turns into a full condition walk for a buyer or an insurer, the pool inspection pricing calculator covers that longer scope and its written report.

Sources: American Leak Detection — Calculate Your Swimming Pool Water Loss in Gallons; Pool Leak Inspections — Bucket Test; PoolDial — Bucket Test Calculator.