Pool Bottom Sinking

[pooladdict]

Hi Everyone:

I had my vinyl pool installed 3 years ago, and now I am noticing alot of shifting in the cement bottom. When they installed it, they easily used 5 trucks of gravel before they put the thin cement in before putting liner down.
I now have several spots where I believe the gravel has settled, cement has fallen and liner has followed it.

Any recomendations?

The PB wont help me at all.

 

[dayhiker]

A leak would be the obvious first thought. Are you losing water?


From a soils standpoint, those glacial tills can be nasty stuff. Did they mention poor soils as a reason for all of that gravel? About how thick was the gravel layer? How thick is the concrete slab?

 

[pooladdict]

There is no leakage at all, the major concern is new drop offs LOL.

THey had to put all the gravel due to pulling out an existing inground pool. We situated ours differently so couldnt reuse the old one.

Its not bad, just some spots where you can feel a definate drop off.

 

[dayhiker]

But for the concrete slab to move the sub base would have to move. For that to move, the soil below would have to move...which leads to the question of what would make all of that move.

When you say dropoff, what do you mean? I'm picturing 2' (670mm) diameter type areas that are maybe 1/2"-1" (12-25mm) lower than the surrounding pool bottom.

I've seen 4" concrete slabs that have been severely undermined with little, if any movement. My 2' diameter comment up there maybe should have been 4'.

 

[pooladdict]

I think you are thinking its a concrete base, most vinyl lined pools either have sand or very thing concrete bottoms, this is the case for mine, I believe the thin concrete gave in to the pressure of all the water and has dropped about 2" in places. Its nothing major now, but could be in the future.

 

[dayhiker]

That's why I asked all the questions...trying to figure out what you meant by thin cement slab. Your description sounded like you had a thick layer of gravel and then a concrete slab. I'm not sure how thin is a thin slab?