Pool losing 1 inch of water per day?
Here's what that actually means.

The most common call we get starts with some version of: "I think my pool is leaking — it's losing about an inch a day." The honest answer is that "an inch a day" covers everything from completely normal evaporation in Florida summer to a serious underground plumbing failure. The number alone doesn't tell us which. What you need is a structured way to figure it out.

First: the math.

Before we diagnose anything, let's get specific about what "1 inch per day" means in actual volume. This matters because water-loss math is what separates normal from not-normal.

So when someone tells us their 18×36 pool is losing "an inch a day," they're actually losing about 400 gallons a day. If it's just evaporation, that's normal for a hot Florida August. If it's a leak, you're looking at 12,000+ gallons a month going somewhere.

Is it evaporation — or a leak?

This is the central question, and the good news is there's a simple, free test that answers it definitively in 24 hours. We call it the bucket test. It's been around forever. Most pool owners have heard of it. Almost no one does it right. Here's exactly how:

The bucket test, step-by-step

1. Get a 5-gallon bucket. Any plastic bucket from a home improvement store. Don't use metal.
2. Fill it with pool water to within an inch of the rim.
3. Place it on the pool steps so the bucket is partly submerged. This equalizes water temperature — critical for accuracy.
4. Mark both water levels. Use tape or a permanent marker. Mark the pool level on the outside of the bucket. Mark the bucket level on the inside.
5. Leave it for 24 hours. Keep the pump running on its normal schedule. Don't swim. Don't add water. Don't touch the bucket.
6. Compare after 24 hours. Measure both drops.

Normal Florida evaporation: what to expect.

This is the part nobody tells pool owners. Florida evaporation rates are not constant — they vary dramatically by season, humidity, wind, temperature, and whether you have a screen enclosure.

So "1 inch per day" on an open, unscreened, heated pool during a January cold snap with wind? Could absolutely be just evaporation. Same number on a screened pool in August with no heater? Almost certainly a leak.

Context matters more than the raw number. This is why a specialist diagnostic always starts with questions about pool enclosure, heating, usage, and season — not just "how much are you losing."

If the bucket test confirms a leak: what's next?

A confirmed leak doesn't tell you where. But the pattern of loss narrows the source significantly before a specialist ever arrives. Here's what different patterns usually mean:

Loss only when the pump runs

This is a pressure-side leak — somewhere in the return plumbing or a return fitting. Water is being pushed out of the system under pressure. Common sources: return jet fittings, valve bodies, heater connections, underground return lines.

Loss only when the pump is OFF

This is a suction-side leak or a structural leak below water level. When the pump is off, gravity is pulling water through the leak. When the pump runs, suction reverses that flow. Common sources: main drain, skimmer throat, suction-side plumbing.

Loss about the same whether pump runs or not

Most likely a structural leak — shell crack, tile-line separation, or a fitting in the pool below waterline. Common in older pools or pools showing deck settlement.

Loss stops at a specific water level

The leak is at that exact water level. If your pool stops losing at the skimmer waterline, the leak is at the skimmer. If it stops halfway down the shell, there's a crack at that depth. This is one of the most useful diagnostic clues and one of the easiest to observe.

Should you call a specialist — or wait?

Not every confirmed leak is an emergency. But some are. Here's our threshold:

The reason we push urgency above 1 inch per day isn't about the water cost. It's about the damage escalation timeline. A leak releasing 500+ gallons per day into the ground around the pool is eroding soil, causing differential settlement, and creating conditions that lead to larger structural problems. The repair on an early-caught leak is often 10-20% of the cost of a late-caught one.

Common questions we hear.

"Could it be the auto-fill malfunctioning?"

Sometimes. A stuck-open auto-fill can mask evaporation numbers by constantly topping off. Check your water bill — if it jumped $40-200/month, the auto-fill is covering for a leak. The bucket test bypasses this issue since you're not reading the auto-fill meter.

"What if my pool has a water feature or fountain?"

Sheet-descent features, fountains, and deck jets all dramatically increase evaporation when running. If your pool has a feature on a timer, run your bucket test with the feature set to its normal schedule — not off. Testing with the feature off gives you a misleading baseline.

"I keep topping off — should I let it drop to see where it stops?"

Yes, if you're waiting for a diagnostic appointment. Letting the pool drop until it stops tells the specialist exactly what elevation the leak is at. Just don't let it drop below skimmer level (the pump will start sucking air, which can damage equipment).

"Does homeowners insurance cover pool leak repair?"

Generally no for the leak itself. Policies typically cover damage caused by a leak (water damage to structures, foundation issues) but not the repair of the pool leak itself. We have a full guide on pool leaks and homeowners insurance.

"My pool lost a lot and now it's stopped — did it fix itself?"

Usually, no — what happened is the water level dropped below the leak point. The leak is still there; it just can't leak water it can't reach. Once you refill, the loss returns. This is actually a useful diagnostic: the elevation where loss stopped is the elevation of the leak.