Rapid drop in water level and then stable again


New member
Jan 25, 2015
Can someone please explain to me what is happening here. It is a bit strange. Twice I have left the garden hose filling the pool and forgot about it. Both times the water level came right up to the bottom lip of my sandstone coping. Within 24 hours I had found that the water level had dropped by 5-10cm (1.96-3.93 inches). This is quite a lot for a pool that is roughly 10m x 5m.

I've had solar leakage issues in the last week, so I haven't been able to run my pool filter at all. I was surprised that the latest overfilling incident also resulted in a quick drop in water level. Even without the pool filter running.

What is strange is that once it gets to a certain level (5-10cm below the coping), it stops dropping.

Any ideas where the water is going? Can't be evaporation as the have the solar blanket on. I have had a recent resurfacing/renovation (1.5 years ago) to the pool and there are some cracks appearing below the coping. Could the water be going through there? The new concrete render was over the old shell. So I don't understand how water can leak through those cracks. I will post separately on how to repair those cracks.



Gold Supporter
TFP Guide
Nov 12, 2017
Central California
That would happen just like that in my pool because I have an overflow outlet that prevents water from getting any higher than a pre-determined level. Is it possible your pool has such a feature? That would drain water quickly then stop, just as you describe.

When I recently resurfaced my pool, the pebble guys completely re-did my returns, replumbing them with threaded ends and adding eyeballs. Never mentioned that in my contract, they just did it. Maybe your guys added something like that if it wasn't there before?