Pool leak vs. evaporation.
How to actually tell the difference.

Florida pool owners see dramatic evaporation most of the year. On a hot summer day with wind and low humidity, a half-inch of water loss is unremarkable. A first-time pool owner watching that happen understandably wonders if they have a leak. A seasoned specialist looks at the same pool and knows instantly whether it matters. The difference is understanding what drives evaporation and what doesn't.

What drives evaporation.

Evaporation is a function of the difference between water temperature and air temperature, the humidity of the air above the water, and how much that air is being replaced by drier air (wind). More heat on the water, drier air above it, and more wind moving that air away — all increase evaporation. Here's how the key factors weigh:

Typical Florida evaporation rates,
by season and conditions.

These are the rates we've observed across 100,000+ diagnostic appointments. They're rough guidance — your actual rate varies by specific location, enclosure, and features — but they're the baseline against which to compare your own loss.

Important note: these numbers are worst-case for the condition described. Most days fall in the middle of each range. The specific confluence required to hit the upper end (wind + heat + dry air + unscreened + active water features) is relatively uncommon.

The bucket test:
the only truly reliable answer.

Every other method of evaluating pool water loss involves guessing at evaporation rates. The bucket test bypasses the guessing. Because the bucket and the pool share the same weather, temperature, humidity, and wind conditions over the same 24 hours, the evaporation from both should be identical. Any difference is leak loss.

We've written a detailed walkthrough in our 1-inch-per-day guide. Short version:

1. 5-gallon bucket, filled with pool water, placed on the top pool step.
2. Mark the water level inside and the pool level outside.
3. Wait 24 hours with normal pump operation.
4. Compare drops. If the pool drop is greater, the difference is leak loss.

Two situations where the bucket test alone isn't enough:

Variable water features

If your pool has a waterfall, spillover spa, or deck jets that run on a timer, the test needs to reflect normal conditions. Run the test with features set to their regular schedule. Testing with features off will show low evaporation and make a small leak look larger than it is.

Intermittent leaks

Some leaks only leak under specific conditions — pump running, heater active, specific water level, spa spilling over. A 24-hour test that doesn't include the triggering condition can miss the leak entirely. If bucket tests are ambiguous across multiple trials, that's a clue toward an intermittent pattern.

When evaporation looks like a leak.

There are specific scenarios where normal evaporation gets mistaken for a leak — some of our most common second-opinion calls start here:

Scenario 1: New pool owner in summer

Owners who bought homes in spring don't see their pool's summer evaporation rate until July-August. The sudden jump from 1/4 inch to 1/2+ inch per day feels like something broke. Nothing broke — the weather changed.

Scenario 2: Heater added to existing pool

Adding a heater can double your pool's evaporation rate. Owners call convinced the heater installation caused a leak. Usually it just exposed normal heated-pool evaporation numbers.

Scenario 3: Screen enclosure damaged or removed

Hurricane damage, renovation, or removal of a screen enclosure can roughly double evaporation. Pools that evaporated 1/4 inch before are now doing 1/2 inch, and owners understandably assume the damage caused a leak.

Scenario 4: New water feature installed

Adding a waterfall, spillover, or bubbler adds significant surface evaporation. A new "leak" that appeared right after a remodel is often just the features doing what features do.

Scenario 5: Vacation home that was recently used

Vacation owners who refill before arrival, use the pool heavily, and leave often see "losses" that are really splash-out plus normal evaporation during heavy use. The pool stabilizes after use returns to normal.

When the bucket test says evaporation,
but it doesn't feel right.

Occasionally a client runs a bucket test that shows even evaporation, but they're still convinced something is wrong. In most cases, the bucket test is right — but here are the legitimate exceptions:

Test duration too short. A 24-hour test can miss small, slow leaks. Running the test over 72 hours increases sensitivity to fractional-inch differences.

Bucket placement inconsistency. If the bucket is in shade and the pool is in full sun (or vice versa), results are misleading. The bucket should experience the same sun exposure as the average of the pool surface.

Marking error. 1/16-inch differences are within the margin of human marking error. True leaks of that size are rare but exist.

Visible damage signs. If you see wet spots around the pool, dying grass, deck settlement, efflorescence on retaining walls, or air in the pump basket — trust those signs over a bucket test. They indicate a leak regardless of what the bucket shows.

The bottom line, briefly.

If your pool is losing water, the first question is never "what's the leak source" — it's "is there actually a leak, or is this normal evaporation for the conditions I'm in?" The bucket test answers that question definitively in 24 hours. Once you know the answer, you know what to do next. If it's evaporation, no action needed — maybe a cover investment for the thirsty months. If it's a leak, the pattern of loss narrows the source, and a specialist can usually find and fix it faster than most pool owners expect.