Need help with infinity pool water levels


New member
Jun 7, 2021
Los Angeles,CA
Hello, new to the forum. I'm currently at a client's home doing general repairs. I don't know much about pools but I would like to help them with some concerns they have as they think there's a leak in their infinity pool. Specifically in the catch basin. Some days the water level in the catch basin is low, other days higher and overflows out of the leveler tank. When the pumps are on, the water in the catch basin goes down several inches, when they turn off, the water in the catch basin goes up slowly through the day until it overfills the overflow tank. Is it normal for water in the catch basin to continue to rise after the pump shuts off? The check valves look closed at the pumps. Thanks for any help and ideas.


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Gold Supporter
May 2, 2021
Pool Size
Salt Water Generator
I'm new here so keep that in mind...

I have a disappearing edge on my pool that holds about 1600 gallons. Water flows over the top of it (over the coping pavers) and into the lower pit (that's what I call it at least). The pit has two drains in it that run back to a single pump, which pulls water out of the lower pit and sends it atop the waterfall, which cascades down, flows back into the pool, and then flows over the disappearing edge back into the lower pit (think of it as a closed loop system).

I noticed that, when the pump was turned off, the lower pit's water level would rise on it's own around 1" an hour (even if the water cascading over the disappearing edge and over the coping pavers), which may not sound like a big deal, but it actually is for a variety of reasons). At first I suspected the water was coming back into the lower pit from the 2 drains where the pump sucks water out, and was potentially back-flowing into the lower pit from the drains so I had the check-valve replaced (whatever that valve is called that stops water from going in the reverse direction). But that still didn't fix it, and anytime that pump was off, I'd tsill gain roughly 1" per hour in the lower pit.

It turned out that water was getting into the lower pit from mortar cracks that were roughly 1-2" underneath the coping pavers themselves between the main pool and the lower pit. In short, anytime the main pool's water level was at normal level (or within 1-2" of normal level) water was getting into the lower pit, not just from going OVER the pavers like it's designed to, but because the water was even going UNDER the pavers in cases where it wasn't high enough to flow over the top of the coping pavers.

To fix it, I needed to re-mortar all the coping areas that lead to the lower pit from the main pool (re-mortar both the pool side -and- lower pit side, not just one side!!) Once I did that, I no longer saw a 1" per hour increase in the lower pit's water level when the pump that sucks water OUT of the pit was turned off.

Not saying that's your issue but, ugh.., that one issue took me about 1-2 months to actually track down.

QUICK EDIT: I should mention, my pool is about 10-11 years old now, so cracks in mortar are becoming more common due to its age and I need to re-mortar even MORE areas than just the one area I fixed leading to the lower pit. but I think you should check this at least, because your symptom is very similar to what mine was , especially relating to when the pump is on/off!


Gold Supporter
May 20, 2020
Katy TX
Pool Size
Liquid Chlorine
Couple of thinks to consider.
First, you made no mention of a skimmer in the catch basin, so the only suction is via the drains on the bottom of the catch basin?

If no skimmer then the only access to the catch basin is via the 2 suction lines. The picture of the plumbing show 2 pumps so they have 2 pumps for suction from the catch basin which creates the infinite edge? Downstream of the check valves there are manual valves. Have you turned those closed after the pump is turned off to monitor the flow back to the catch basin via the suction line? This would help determine if the check valves are leaking back. What is not shown is the level of the pump vs the level of the pool and the level of the catch basin. That suction line will want to balance out under static conditions unless there is a check valve in another place other then downstream of the pump. Do you know the height differences of these levels?

You mention a overfill tank and the picture seems to show a float system that controls that level in the catch basin. Have you verified that the float valve is shutting off completely?

If there is no leak from the pool to the catch basin as a possible issue noted by @jesser then it seems to be a hydrostatic issue or leaking check valves and/or float valves.


New member
Jun 7, 2021
Los Angeles,CA
There is no skimmer at the catch basin. Theres 2 pumps for the 4 succion drains but only 1 turns on. I turned off the pump ball valve only, not all of them. The pump is in a basement lower than the pool itself. The float in the overfill tank shuts off but the rising water in the catch basin continues to rise and overfills the tank. A lot of pool tiles especially around the infinity edge are falling off already. This pool is about 7 or 8 years old. Maybe water is making it's way through there. Is there a way I can verify this? I will try all your recommendations tomorrow morning. Jesser's issue seems to be almost dead on. Today the pool cleaner said the water in the pool was lower than usual and the catch basin was also a bit lower. There is some algae buildup in some areas more so than others not sure if that's a clue. A leak detection guy came over last week and said it was the float valve. So it was replaced and once it shuts off it still would overfill at the overfill tank. Owner says the pool has been leaking at the overfill tank for years. Thanks so much for the replies and suggestions.
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