Sagging/Sinking Concrete Pool Deck

[chrisnkeri]

We just had a 20x40 inground liner pool installed in the fall. We have 7.5 feet of concrete on both long sides with 10 foot on each end. On one side of the deep end, our concrete has cracked separated and dipped in that area. Before we removed the winter cover, we had a concrete/foundation specialist come out and take a look. He says we could inject some of the leveling foam under the sunken area and that would do it. A few days after, our pool guy came over to open our pool. They removed the cover and dumped some chemicals and left. Our water level was a little low, so we had to add more water. He told us where on the skimmer we should raise the water level, but the more water we added, the more I noticed that the water didn't hit the liner evenly around the pool, mainly on the cracked concrete side. I measured and on the good side with the skimmer, the water was about 7 inches from the coping and on the bad/cracked side we were about 5 inches from the coping. My question is, would just a cracked/sagging pool deck cause the water level to be different? Would foam fix the problem? Or could it be that the footer for the pool wall has shifted? I have a couple of pictures from a distance the crack is on the far left side. I will post more of the actual crack a little later.

 

[JohnT]

Welcome to TFP!

I hate to say it, but that doesn't sound good at all. Concrete that sinks is generally because the material supporting it isn't compacted. Chances are they backfilled with soil or the backfill material has washed.

 

[duraleigh]

+1 what JohnT said. That's on your PB if he did the backfill. The concrete guys don't care (nor can they tell) if the substrate hasn't been compacted properly.

If your skimmer has shifted, the line from it may well be cracked causing a leak in the pool.

 

[gwegan]

+2 to what John said above. It sounds like the soil under your pool wall has sunk. It may be fill or it may be weak soil we don't know. There is generally not a footer under vinyl liner pool walls there is a poured concrete "footer" behind the wall. I'd have your pool builder out for a long hard talk about the problem.

 

[PAGirl]

Was the property recently developed? I.E. Has it not been too long since the whole area was made level/graded?

 

[chrisnkeri]

They backfilled with a mixture of gravel sand and dirt. We don't think it was properly compacted before the concrete. Since you asked about the area, here is what we ran into while digging for the pool.....

That is a wall from a sileage pit that we had to have broken up and removed, which is right where the crack and sinking concrete is

 

[gwegan]

Yea that could be a problem if the replacement soil was not properly installed and compacted.

 

[440dodge440]

I assume these are still the remains of the wall in the area not dug up...I wonder if it's causing water to pool underground, creating a mud pit 3 feet down that's not able to take much load on top. The pool would probably block the open side the was excavated....Does the silage pit have a concrete bottom, or does it go straight to dirt?