Pool auto-fill
Why does my pool auto-fill never shut off?
An auto-fill that runs constantly is either a failed float valve that has stopped closing, or a working valve doing its job on a pool that is losing water faster than it should. Those two look identical from the patio, and telling them apart takes a minute at the valve and three days at the tile line.
What it usually is
A valve that will not close, or a pool it cannot keep up with
An auto-fill that runs all the time usually means either the float valve has failed to seat, or the pool is leaking at about the rate the auto-fill supplies.
An auto-fill is a small float valve in a deck box, plumbed from the house supply. The level falls, the float drops, the valve opens; the level returns, the float rises, the valve closes. There is very little to it, which is why there are few ways for it to fail.
Valves fail here for reasons that have nothing to do with the pool. Hard water leaves deposits on the seat so it no longer closes cleanly, blown grit works underneath it, and sun on an uncovered lid ages the plastic until the linkage no longer travels. Any of those leaves a valve that trickles forever.
Be honest about it
What it could be instead
Three things imitate a runaway auto-fill and need no repair at all:
- The box is full of runoff. Irrigation or storm water in the box holds the float at a height that has nothing to do with the pool.
- The valve is set for a level the pool no longer sits at. After a resurface or new tile, the intended level can change.
- It is not the auto-fill you can hear. A hose bib barely cracked open or an irrigation valve weeping makes the same quiet trickle in the same corner.
Look in the box first.
Narrowing it down
Telling a failed valve from a leaking pool
| After you close the auto-fill | What it means | What to do next |
|---|---|---|
| The pool holds its level for days | The pool is sound; the valve was the problem | Service or replace the float valve, then reopen it |
| The pool starts dropping steadily | The auto-fill was masking a real loss | Mark the level and run the bucket test both ways |
| Water still runs in the box | The fault is upstream of the float | Close the supply feeding the box and look at the line |
Ten minutes, on your own
The one-minute check, and the three-day check
The first tells you about the valve. The second tells you about the pool.
Lift the lid and look
Scale on the seat, a corroded arm, grit, or a box full to the brim are all visible straight away.
Close the auto-fill shut-off
Usually a small valve on the supply into the box, or a dedicated one at the equipment pad. Write yourself a note.
Mark the pool level on the tile and note the time
This is where the auto-fill question turns into the pool question.
Read the mark after a day, and again after three
A pool that holds had a bad valve. A pool that drops was being propped up, and the bucket test is next.
How urgent is it
Not dangerous, but it hides things
Nothing about a running auto-fill threatens the house.
What it does is erase evidence. A falling level, a line that stops at one height, a loss that tracks the pump schedule - every one of those signs is wiped out by a valve that keeps topping the pool up. Closing it is worth doing today.
If you call us
What we look at
If the pool holds with the auto-fill closed, the job is the valve and the small amount of plumbing around it, and we will tell you that rather than sell a detection visit.
If the pool does not hold, the auto-fill was the symptom and the pool is the job: lines isolated and pressure tested, acoustic listening on anything that will not hold, dye at the shell fittings. That is pool and spa leak detection.
Straight answers
Auto-fill questions
Is a constantly running auto-fill a sign my pool is leaking?
It can be, which is the reason to test rather than adjust. Close the auto-fill and mark the pool level. If the pool holds for three days the valve had failed; if it starts dropping, the auto-fill was covering a real loss.
Can I just leave the auto-fill closed?
For a few days while you test, yes, as long as you keep the level above the skimmer mouth by hand. Leaving it closed permanently in Valley heat risks the pump losing prime.
Why do auto-fill valves fail so often here?
Hard water leaves deposits on the valve seat, blown grit works under it, and sun ages the lid and the linkage - ordinary wear for a small valve in a deck box in the desert.
The auto-fill runs and the pool level is still falling. What now?
The loss is faster than the valve can supply, which points at a real leak rather than a valve fault. Turn the pump off if the level is near the skimmer mouth, and have it looked at rather than waiting.
Tell us what the water is doing
Whether the pool held its level with the auto-fill closed, and for how long.
Send a photo of the open box
The inside of the auto-fill box, and the pool level against a mark.
5.0 on Google
What customers in the Phoenix valley have written. The words are theirs, on listings we cannot edit.
“Humberto has been amazing! Prompt, professional, and patient. He has gone above and beyond, taking the time to show me how to operate the water valves and educating me so I can continue to monitor for future leaks. He identified multiple leaks and made thoughtful recommendations.”
“Beto was very professional, thorough and patient in explaining everything he was doing and why. It was an excellent and well worth it experience, and this is saying something for an architect who had a hundred questions!”
“The owner and operator of this company is everything a contractor should be. On time, honest, competent, reachable, comprehensive. Hope to work with him again in the future.”