How Much Evaporation a Pool Heater Causes in Winter (Florida Pools)

Quick Answer: How Much Water Loss Is Normal in Winter?

Every backyard is different, but for a typical Florida pool in winter, these are reasonable ballparks
when you’re running a heater:

• Heated to the low 80s, no cover, calm conditions:
  Around 1/4" per day of water loss isn’t crazy.
• Heater + daily spa spillover or fountain:
  It’s possible to see 3/8"–1/2" per day in the right mix of cool, dry, breezy weather.

If your water level is dropping a little faster when you’re actively heating the pool and running features,
that alone doesn’t mean you have a leak. It may just be the cost of keeping a “resort feel” in January.
But if you’re going past 1/2" per day on mild days with features off, it’s time to get more serious.

For the bigger picture on “normal vs leak,” see:
Normal Pool Water Loss vs a Real Leak (Florida Guide).

Why Heated Pools Lose More Water in Cool Weather

Even without a leak, a heated pool in winter will lose more water than the same pool sitting cold.
The reason is simple: the bigger the temperature difference between the water and the air,
the more the water wants to evaporate.

• Warm water + cool air: When your pool is 84°F and the air is 55–60°F, you’ll often see
  visible steam and faster evaporation.
• Heater run time: Running the heater for long stretches keeps that temperature difference going,
  so evaporation doesn’t really get a break.
• Cool, dry nights with a breeze: Those “chilly but nice” Florida evenings pull water off
  the surface faster than most people expect.

That means a pool that barely budged in August can suddenly start dropping in December–February,
especially on nights where you can see steam rolling off the surface.

How Spa Spillovers and Water Features Supercharge Evaporation

Now add in water features and the effect gets even stronger. Things like:

• Spa spillovers that trickle or pour into the pool all day.
• Fountains, bubblers, and deck jets throwing water into the air.
• Sheer descents and waterfalls running for “ambience” every evening.

All of these do the same thing physically:

• They break the water up into droplets and thin sheets.
• They throw that water into the air, where it has more surface area exposed.
• They keep the surface “busy” instead of calm and glassy, which slows evaporation down.

A calm, still pool will always evaporate less than a heated pool with a constant spa spillover
and a couple of fountains running. The more splash, spray, and aeration, the more evaporation—especially when
the air is cool and dry.

The key thing to remember: heaters and features don’t create leaks, they just make any normal
evaporation (or existing leak) show up faster.

DIY Checks: Is It the Heater/Features or Something More?

Before you panic about a leak, you can run a simple “A/B test” on your own pool to see how much loss
is linked to the heater and features.

1. Step 1 – Everything off: Turn the heater off and shut off spa spillovers and
   fountains for 24–48 hours. Mark the waterline with tape or a pencil mark on the tile and see how far it drops.
2. Step 2 – Heater on, features off: Heat the pool like you normally would, but leave spillovers
   and fountains off. Mark the level again and compare the drop.
3. Step 3 – Heater + features on: Run the heater and features how you normally like them.
   Mark the level and see how much faster the water falls with everything running.

This quick comparison tells you how much of the loss is coming from heater + water features
versus a possible plumbing or shell issue.

For a broader self-check that covers summer and non-heated pools too, see
Evaporation, Splash-Out, or Leak? Quick Self-Check for Homeowners.

Use the Bucket Test to Separate Evaporation from Leaks

If you still aren’t sure, the classic bucket test works just as well in winter as it does in summer.
It compares your pool against a small “mini-pool” that can only lose water to evaporation.

1. Fill a bucket about 3/4 full and set it on the second step.
2. Make a small mark on the inside of the bucket at the water level.
3. Make a matching mark on the pool tile at the pool water level.
4. Run the pool the way you normally do (heater on or off, features however you usually use them) for
   24 hours.
5. After 24 hours, compare how far the water dropped in the bucket vs. the pool.

• If the pool and bucket dropped by about the same amount, you’re probably seeing normal evaporation
  for your conditions.
• If the pool dropped significantly more than the bucket—especially with heater and features off—
  that points toward a real leak, not just evaporation.

For a full walk-through, see
How to Do a Bucket Test for Pool Leaks (Step-by-Step).

Red Flags That Go Beyond Normal Winter Evaporation

Even with a heater and spa spillover running, these signs usually mean it’s time to call a pro instead of
blaming everything on evaporation:

• You’re losing more than about 1/2" per day on mild days,
  even when the heater and features are off.
• You see soft spots, constantly damp areas, or settling in the yard or along the deck that stay wet.
• The pump loses prime or pulls a lot of air, especially on startup, or you see air bubbles in the pump basket.
• You notice cracks around the skimmer, tile line, or lights that seem to pull dye or show movement.
• Your autofill runs constantly and your winter water bill is way higher than expected.

Heaters and features can speed up evaporation, but they don’t create soft soil, hollow-sounding decks,
or air in the plumbing. Those are classic leak clues.

When It’s Time to Call a Leak Detection Pro

If your tests show the pool is dropping faster than the bucket, or you’re seeing any of those red flags, it’s smart
to get a professional leak detection visit on the books. A good Florida leak detection tech will:

• Pressure-test the plumbing lines to rule out underground leaks.
• Dye test skimmers, returns, lights, and suspicious cracks in the shell.
• Check the equipment pad for hidden drips or slow failures.
• Explain how much of your water loss is normal evaporation versus an actual leak.

If you don’t already have “your pool person” for leaks, start with:
Florida Pool Leak Detection — County by County Guide.

Related Deep-Dive Guides

Want to go deeper on specific parts of this? These focused guides can help:

• Normal Pool Water Loss vs a Real Leak (Florida Guide)
• Evaporation, Splash-Out, or Leak? How to Tell the Difference
• How to Do a Bucket Test for Pool Leaks (Step-by-Step)

Bottom Line

Heaters, spa spillovers, and fountains will absolutely make a Florida pool lose more water in winter—even without a leak.
But they shouldn’t turn your pool into a bottomless pit. By comparing drops with features on and off, running a simple
bucket test, and watching for red flags around the deck and equipment, you can tell when it’s just normal evaporation
and when it’s time to bring in a leak detection pro.