Water loss on infiniti pool

[swimboy24]

So I don't fully understand the plumbing on my infinity pool. I understand the basic concepts (a catch basin that then flows back up into the pool when pump runs). So yesterday the pump wouldn't prime. I called a pool guy after I tried everything I could think of without success. He said it was a dirty filter. I wasn't convinced. He cleaned the filter and the pump did actually prime. But I still wasn't convinced bc I have been watching the pressure gauge on the filter since I last cleaned it and it hasn't risen. And physics is physics.

After he left, I had to leave town for a day. I wasn't convinced so I left the filter in service mode so it wouldn't run dry while I was gone (I knew my chemicals were perfect and so should be fine). I arrive home this evening to find half of the pool empty of water!!!

I see only two possibilities for this:
1) There is a leak.
2) Somehow the water flowed backwards from the pool into the catch basin and then out the side wall which is the catch basin overflow.

One pic is the amount of water that was lost. The other is the wall where the catch basin overflow is. I mainly worry about the water that seems to be coming out of a crack and onto the wall. There is no rain here (in LA) and no sprinklers over there... so no way that all should be wet. But the house (and pool therefore) is only 2-3 years old so not sure how I'd get a leak so quickly minus a major earthquake. Thank you for any ideas!

And as a follow up... I see no reason to add more water other than the post I read about draining a pool potentially leading to concrete cracks. But I also feel that ship would have already sailed. Because if it lost that much in a day, I don't expect it would hold water if I put it back in.

 

[ajw22]

Show us pictures of your equipment pad, valves, and how you put your filter in SERVICE mode.

Where does the catch basin pump return the water to in the pool? Show us.

 

[swimboy24]

Show us pictures of your equipment pad, valves, and how you put your filter in SERVICE mode.

Where does the catch basin pump return the water to in the pool? Show us.

I'll take pictures in the morning (hard to see at night). The equipment is pretty straightforward: 4 Intake sources: vacuum connections, 2 floor drains and the catch basin... all lead to the pump then to the cartridge filter and heater and back out return into the pool. The pump service mode I put in manually.... I have the aqualink app but on the control panel, you just hit the service mode so pump doesn't run. But will take photos in the daylight.

What I don't know is exactly how the plumbing works from catch basin back to pump because all of that is in the cement and not accessible. Just a pipe coming back out of the cement.

 

[ajw22]

Please put Aqualink in your signature along with your pump model and heater model and any mother equipment not listed.

You can figure out where the catch basin water comes back into the pool.

 

[JoyfulNoise]

That much water should have left its mark on the property somewhere. Did you see any soggy ground anywhere ?

Also, there better be a check valve between the basin and the pool or else gravity (physics again ) wins …

PS - Cartridge filters have very low head loss and many will register very little pressure when clean. They also can load up quite a bit causing a loss of flow with very little change in pressure at the gauge. So don’t totally discount a dirty filter making it harder to prime a pump.

 

[swimboy24]

I will update the signature soon. But I think it is not a leak. I think it is somehow backflowing into the catch basin. I say that because the catch basin is full. If I put a hose in the catch basin and turn it on, water goes out the overflow house and down the hill.

I've attached a few more photos. The first one just shows where the water returns into the pool... there are 3 inlets... as you can see by the markings on the bottom of the pool. The second shows the pump platform. The lines that flow into the pool from left to right: 1) vacuum (with blue valve) line 2) catch basin return (with janky valve) 3 and 4) floor vents.

The only thing I can think is that both one direction jandy valves are incompetent and allowing flow to go back into the basin. And if it is a closed system, it would work like a syphon. Does that seem possible? I struggle bc I opened up the jandy valve just proximal to the filter the other day and cleaned out the leaves and stuff that were stuck in it. And it seemed to be working just fine. Unless they are somehow more complicated than they appear haha.

I closed the valves so that the catch basin flowed back into the pool. Waited until air just started showing up and then switched to just recirculate in the pool. So now the catch basin is empty essentially and I figure I am going to leave the pump on and watch the water level (which I marked). Then I'll turn the pump off and see if the water level falls. Seem reasonable? If it falls while running, then something else is wrong.

Regarding wet soil... that's a tough one. Because the overflow outlet is on the side of the hill I'm on. Yes, it is moist over there.... but it is a rocky hill so any water would have rolled down into the gutter. And unfortunately uphill neighbors waste water into the gutter too often to know if it was from mine or theirs.

Also, to test my theory, before I did this all, I opened the pressure relief on the top of the filter... and it clealy had negative pressure and was sucking in air. More reason to think it is back flowing somehow. Now the question remains... how.