Autofill Never Shuts Off? How to Tell If It’s Hiding a Pool Leak

What an Autofill Is Supposed to Do

A pool autofill is basically a toilet float for your pool. When the water level drops a bit, it opens and
lets in fresh water. When the level comes back up, it closes.

In normal conditions, you might hear it kick on occasionally after a hot, windy day, a big pool party, a heater
run, or a week with no rain. What you shouldn’t hear is a constant trickle with no obvious reason.

Signs Your Autofill May Be Masking a Leak

Watch for patterns like these:

• You hear the autofill running almost every time you walk past the pool.
• Your water bill has climbed without a big change in household use.
• The waterline always looks “perfect,” but you are constantly paying for extra water.
• The pool never looks low, but the autofill basin or fill line is always active.
• You notice soft ground, wet spots, or an equipment pad that stays damp.

Because the autofill keeps the pool topped off, you never see the level drop. Instead, the leak and the
autofill quietly work against each other all month long — and you pay for the lost water.

How to Test the Pool Without the Autofill’s Help

To see what the pool is doing on its own, you need to take the autofill out of the equation for a short time.
If you can safely do it:

1. Turn off or temporarily block the autofill so it cannot add water.
2. Bring the water to your normal level and mark the waterline on the tile or wall.
3. Note the weather and whether the pump is on or off.
4. Wait 24 hours and mark the waterline again.
5. Compare the pool’s drop to your bucket-test result.

For better data, combine this with a
bucket test
so you can compare the pool’s drop to a small container of water in the same conditions.

If the pool drops aggressively once the autofill is off — and that drop is clearly more than the bucket —
you are no longer talking about normal evaporation.

What to Do If the Autofill Confirms a Leak

If the test shows heavy loss without the autofill’s help:

• Document the amount of loss over 24–48 hours.
• Note whether the pump was on or off during the test.
• Inspect the equipment pad and surrounding yard for soggy spots.
• Look for a stop level if the water keeps dropping and then parks at one height.
• Take a photo of the waterline marks before and after the test.

That information is extremely valuable if you decide to call a leak detection company. It also helps you decide
how urgent the situation is — small, slow loss vs. heavy, fast loss.

Related Guides

• 
  Bucket Test Results Explained
  

Bottom Line

An autofill that never seems to shut off is more than an annoyance — it is a warning. By turning it off briefly,
marking the waterline, and running a simple bucket test, you can see what the pool is really doing and whether
you are quietly feeding a leak.

Once you know how fast the water is disappearing without the autofill’s help, you can decide whether it is time
to call in a leak detection pro or tighten up your evaporation and splash-out checks.