A pool loses water for two reasons: evaporation or a leak. Normal summer evaporation runs 1/4 to 1/2 inch per day; anything more than 1 inch per day in shade is usually a leak. The bucket test distinguishes the two in 24 hours: fill a bucket on the top step, mark the levels inside and outside, and compare drops the next day. Most "leaks" turn out to be loose returns, a cracked skimmer throat, or a worn pump seal o-ring, all cheap fixes. Real plumbing leaks are rare and usually live under decks or at pool light niches. This is the operator playbook for water loss complaints in 2026.
TL;DR
- Normal evaporation: 1/4 to 1/2 inch per day in summer, less in cooler months and shaded pools
- The bucket test distinguishes evaporation from a leak in 24 hours
- Most "leaks" are loose returns, cracked skimmer throats, or worn pump seal o-rings (cheap fixes)
- Real plumbing leaks are rare; usually under decks or at pool light niches
- Pool loses more than 1 inch per day and bucket test confirms a leak: time for a leak detection specialist ($200 to $400)
- Plumbing repairs run $400 to $4,000 depending on access and severity
The bucket test
The bucket test is the universal diagnostic for "is this evaporation or a leak". The setup takes 5 minutes; the result is 24 hours.
- Step 1: fill a 5 gallon bucket with pool water to within 1 inch of the rim
- Step 2: place the bucket on the top step of the pool, partially submerged so the bucket water and pool water are at the same temperature
- Step 3: mark the water level on the inside of the bucket AND the outside (the pool water level relative to the bucket)
- Step 4: wait 24 hours with the pump running on normal schedule
- Step 5: compare the two levels. If both dropped the same amount, evaporation. If the pool dropped more than the bucket, you have a leak
“The bucket test is free, takes 24 hours, and tells you definitively if there is a leak. Run it before any other diagnostic.”
How much evaporation is normal
A typical residential pool loses 1/4 to 1/2 inch of water per day to evaporation in summer. In hot dry markets (Phoenix, Las Vegas) summer evaporation can hit 3/4 inch per day during heat waves. Pools with running water features evaporate faster. Pool covers cut evaporation by 70 to 95%.
Anything beyond about 1 inch per day, even without a covered pool in extreme heat, suggests a leak. Below 1/4 inch per day is unusually low and might indicate a cover was left on or shade is heavy.
Common leak sources
Most leaks are not the pool shell or plumbing; they are at fittings and seals.
- Loose returns or skimmer throat caulking (cracked, separated). Easiest fix, $20 to $80 in caulk and labor
- Pump seal o-ring or shaft seal. $40 to $150 in parts
- Filter tank o-rings or unions. $20 to $80
- Pool light niche seal. $200 to $400 (drain not required for some fixes)
- Skimmer crack (chase the crack from inside the pool, fix with pool putty or replace). $100 to $400
- Underground plumbing leak (rare). $1,000 to $4,000 depending on depth and access
How a leak detection specialist works
If the bucket test confirms a leak and you cannot find the source visually, the next step is a leak detection specialist. They use pressure testing, dye testing, listening devices, and underwater video to pinpoint the source without excavating.
Cost: $200 to $400 for the diagnostic, payable regardless of whether they find a fixable leak. Repair is separate and depends on what they find. For most service operators, this is a referral relationship rather than a service you provide.
Telling the customer
Frame water loss conversations carefully. Customers default to worst case ("my pool is broken"). The operator who runs the bucket test and reports back "actually this is evaporation, here is what is normal in your climate" builds trust. The operator who shrugs and says "could be a leak, you should call a specialist" before doing the test loses credibility.
Always run the bucket test first. Always.
Pool cover ROI for customers losing water
For customers in evaporation-heavy markets, a pool cover (solar blanket, retractable cover, or auto cover) typically pays back in 12 to 24 months from water savings alone, longer in markets with cheap water and shorter where water is expensive or rationed. Solar blankets: $100 to $400. Auto covers: $5,000 to $20,000. Most residential customers go with solar blankets.
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