Pool Evaporation vs Leak Test Calculator (Bucket Test)

Losing water and not sure if it's evaporation or a leak? Run the bucket test and enter the two level drops here.

Tip: calculate your exact volume on the pool volume calculator first, then bring that gallons number here.

How the bucket test works

Fill a bucket with pool water and set it on a step so the inside and outside levels start equal. Mark both. Wait a day or two with the pump running normally, then compare. Evaporation affects the bucket and the pool equally, so if the pool dropped more than the bucket, the difference is a leak. Enter both drops to see the verdict, and add your surface area to estimate gallons lost per day.

How the leak-vs-evaporation test is calculated

Run a bucket test. Float a bucket of pool water on a step so it sits at the same level inside and out. Over the same period, water in the bucket only evaporates, while the pool loses water to both evaporation and any leak.
Compare the two drops. Subtract the bucket's drop from the pool's drop. The bucket drop is pure evaporation; the difference is the suspected leak.
Judge the excess. Within about 1/16 inch is just evaporation. More than that points to a possible or likely leak worth investigating.
Convert excess to gallons (if area known). Multiply the excess inches by the surface area to express the daily loss in gallons, which makes a small leak concrete.

Worked example

If the pool drops 3/4 inch but the bucket only drops 1/4 inch, the 1/2 inch difference is beyond evaporation — on a 512 sq ft pool that's roughly 160 gallons a day, a likely leak.

Questions

This tool, explained

A quarter-inch a day is common in warm, dry, or windy conditions. The bucket reading is your true evaporation rate for the test period.

If the pool drops more than about a quarter-inch beyond the bucket over the test, treat it as a likely leak and investigate fittings, the equipment pad, and the liner.