"Channel" with soft spots under liner

[LaurenB]

Hi all.

I have an 18x32 Oval semi-inground pool (built into a hill... One side is level with the ground, other side is completely above).

It was installe less than a year ago, so still under warranty.

I few days ago we discovered a "channel" that has formed, presumably over winter, in the bottom. The liner sinks down anywhere from 1-3" into this channel. It is about 2" wide and runs about 25 feet along the length of the pool.

I already notified my builder, just waiting for someone to come out and check.

I would like to clarify that this is not a small dent from foot prints, I have some of those. This is like a river winding along.

Yesterday my husband and I got in and felt along it (most of it is relatively solid, slightly softer than the rest of the bottom). However, we found a couple spots where if you lightly press, you can tell the liner is not supported by anything! You can feel the sand in most spots but in the deepest parts it feels like a trampoline!

I have not noticed any water loss (only minimal from evaporation) so I don't believe there is a leak.

I'm new to pools but I'm guessing something is very very wrong?!

 

[Divin Dave]

It sounds to me like when the pool was installed, sand was used as material for be bottom, under the liner.
And water has washed out a path through that sand.

Im afraid I dont know a good fix for this.

 

[LaurenB]

It sounds to me like when the pool was installed, sand was used as material for be bottom, under the liner.
And water has washed out a path through that sand.

Im afraid I dont know a good fix for this.

I'm thinking the fact that the liner is unsupported in some spots would be very troublesome down the road. Are they going to have to pull the liner up and re-level the sand?

 

[duraleigh]

It sounds like water has washed out some of your base. That said, I am not so sure your liner bottom is unsupported. Assuming your pool is about 4' deep, an unsupported area of your pool floor (maybe 6" around) is about 28.2 sq inches so (yadda, yadda, yadda) that math works out to a column of water that weigh about 47 lbs on top of that 6"diameter area.

I believe your pool liner has enough flex and movement to stretch or move into that area. It is certainly possible and you still have the issue regardless. Being built into the hill without adequate drainage away from the pool may have been a big factor.

 

[DarrelB]

I had voles do that to me last year, had troughs running everywhere under the pool in the sand. The channels were about 3" wide, and wound all over, never in a straight line.
I ended up removing all the sand and using foam sheeting and a gorilla pad instead.