Evaporation, Splash-Out, or Leak? How to Tell the Difference

The Three Main Causes of Pool Water Loss

Most water loss falls into one (or a mix) of these categories:

• Evaporation – water leaving as vapor into the air.
• Splash-out – water pushed out of the pool by use and activity.
• Leaks – water escaping through cracks, bad fittings, or plumbing.

Understanding the “personality” of each type of loss makes it much easier to tell what you’re dealing with in
your own backyard pool.

How Evaporation Behaves

Evaporation is driven by weather and water conditions. It:

• Happens every day, even if nobody swims.
• Speeds up with heat, wind, and low humidity.
• Increases when the pool is heated or features are running.
• Remains fairly steady once conditions are stable.

If your water loss tracks with hot, breezy days and slows on mild, calm days, evaporation is a major factor.
Typical Florida ranges are about ⅛"–¼" per day in normal conditions and slightly
more if heaters and water features are running.

For a deeper dive on what’s “normal” and what’s not, see
Is My Pool Leaking or Is It Just Evaporation?.

How Splash-Out Behaves

Splash-out is tied to use, not weather. It:

• Spikes on days with heavy swimming, parties, or kids and dogs in the pool.
• Shows up as water on the deck, coping, or surrounding surfaces.
• Can lower the water noticeably after a single busy weekend.
• Is much lower on quiet days when nobody is using the pool.

If you lose a lot of water on days with cannonballs and games, and much less on quiet weekdays,
splash-out is doing most of the work.

How Leaks Behave

Leaks tend to show patterns that don’t match normal evaporation or splash-out. They often look like this:

• Water loss stays high even on mild, calm, low-use days.
• Loss can be tied to the system:
  • Faster when the pump is running.
  • Faster when a spa, waterfall, or feature line is on.
• You may see soft spots or damp areas around the deck or yard.
• The pump may pull air or lose prime.
• The autofill runs a lot just to hold level.

Leaks don’t really care about pool parties or quiet days. They show up as steady or condition-tied loss that
doesn’t match what you’d expect from weather or simple splash-out.

Questions That Help Separate Evaporation, Splash-Out, and Leaks

Ask yourself these questions and match your answers to the most likely cause:

1. Does Loss Line Up with Weather?

• More loss on hot, dry, and windy days?
• Less loss on cool, calm, cloudy days?

If yes, evaporation is playing a big role.

2. Does Loss Line Up with Use?

• Big drops after heavy use, parties, or kids and dogs in the pool?
• Very little drop on quiet days with almost no swimming?

If yes, splash-out is a major factor.

3. Does Loss Line Up with Equipment Operation?

• Loss jumps when the pump runs and slows when it’s off?
• Loss increases only when the spa, fountains, or waterfalls are on?

If yes, a leak in plumbing or features may be the issue, or a mix of leak and evaporation.

Use a Bucket Test to Cut Through the Noise

Because weather and use can overlap, it’s smart to run a
bucket test. This compares pool loss to evaporation in a bucket so
you can see if the pool is dropping faster than it should.

Basic idea:

• Put a bucket of pool water on a step and mark water levels inside the bucket and in the pool.
• Run the pool normally for 24–48 hours.
• Compare how far each dropped.

If the pool and bucket drop about the same, evaporation and splash-out are likely responsible. If the pool
drops noticeably more than the bucket, you’re likely dealing with a leak.

Examples of Each Type of Loss

Mostly Evaporation

A screened Florida pool, no parties, heater off, mild breeze. Water drops about
⅛"–¼" per day, and a bucket test matches the pool. Deck is dry, no soft spots, pump
runs normally. That’s classic evaporation behavior.

Mostly Splash-Out

Busy holiday weekend, kids and friends in and out of the pool, dogs jumping in, lots of water on the deck and
coping. The level is clearly lower after the weekend, but loss slows way down once the pool is quiet again.
That points toward splash-out.

Likely Leak

Water drops closer to ½" per day or more even on quiet, mild days. A bucket test shows the
pool dropping faster than the bucket. You notice damp soil along the outside of the deck and the autofill runs
constantly. That’s a strong leak pattern, not just evaporation.

When to Move from Guessing to Action

It’s normal to watch the waterline for a bit and try to make sense of it. But if you see:

• Consistent loss around ½" per day or more,
• Pool dropping faster than the bucket in testing,
• Visible deck or yard issues (soft spots, new cracks, damp areas),
• Autofill running a lot or higher water bills,

it’s smart to treat it as a likely leak and schedule leak detection rather than chasing
assumptions.

Next Steps

• Run a detailed bucket test if you haven’t already.
• Review the full checklist in
  Is My Pool Leaking or Is It Just Evaporation?
• If the signs point toward a leak, plan a professional leak detection visit before the problem grows (and
  before it affects your deck, yard, or water bill).

Getting clear on whether you’re dealing with evaporation, splash-out, or a leak saves time, money, and
frustration. The sooner you know which one it is, the easier it is to fix.