Is My Pool Leaking? How to Do the Bucket Test
By The Aqualitx team at STEMania · Updated
Every outdoor pool loses water. The question is whether it's losing more than the weather explains. The bucket test settles that in a day, for the cost of a bucket.
How much water loss is normal
Evaporation depends on sun, heat, humidity and wind, so it changes with the weather. A typical outdoor pool loses about a quarter inch a day in summer — roughly 75 to 125 gallons a day from a 500 sq ft surface. A heated pool, a windy yard or a waterfall can push that higher. A cover cuts it sharply.
If you log your water fills in Aqualitx, the dashboard's Water loss card estimates evaporation for your pool from local weather and compares it with what you've added. When the fills run well ahead of the estimate, a "Possible leak" note appears under What to do next.
Rule out the ordinary causes first
- Backwashing sends water to waste. A sand or DE filter can drop the level an inch or more each time.
- Splash-out from a busy week of swimming adds up fast.
- Auto-fill valves quietly top the pool up, hiding real loss — or overfill it if they stick.
- Heavy rain followed by draining back down to the skimmer.
The bucket test
- Set a bucket on the pool's first or second step so it sits in the water. Weigh it down with a brick or a few rocks if it floats.
- Fill the bucket with pool water until the level inside matches the pool's level outside.
- Mark the water line inside the bucket, and mark the pool's level on the outside of the bucket (or on the tile).
- Turn off any auto-fill. Run the pump on its normal schedule.
- Wait 24 hours, then compare how far each level dropped.
The bucket and the pool lose the same amount to evaporation, so:
- Both dropped about the same: it's evaporation. No leak.
- The pool dropped noticeably more (about 1/8 inch extra or more): the difference is leaking out.
Run it a second time with the pump off for the 24 hours. If the pool loses more with the pump running, the leak is likely in the plumbing on the pressure side (after the pump). If it loses the same either way, look at the skimmer, fittings or the shell itself.
Where leaks usually are
- Around the skimmer throat, where it meets the pool wall.
- At return fittings, lights and other wall penetrations.
- Tears in a vinyl liner, often near steps or corners.
- Equipment pad fittings — look for damp ground or drips around the pump, filter and heater.
A dye test can confirm a suspect spot: with the pump off, squeeze a little pool dye or food coloring near it in still water and watch whether it gets drawn in. Past that, a leak-detection service can pressure-test the lines and find leaks you can't see.
Why a leak matters for chemistry too
A leak takes chemicals out with the water, and the fresh water you add dilutes what's left, so you end up adding more chlorine, stabilizer and alkalinity than usual. If your doses have crept up and the pool keeps needing water, run the bucket test.