how does water get behind liner??>>>

we've dealt with this since we moved into this home with pool 12 yrs ago, its not a big problem, and we just use a pump behind liner to remove once or twice a season. Property is much lower at the back where pool is , so its due to water table etc. But, I got wondering yesterday when I watched a pool installation at a friends....where does the water come from if the walls are steel?>>>> does it seep through the area where steel meets the concrete floor under the liner? if so is that something that can be corrected when we replace the liner eventually?....I guess I should have just asked the guys who were working, but thought about it too late!

we built our own pool a few years ago. The water came through the seams and under the wall. Dont ask how. We are now building again with a company who is almost done after 6 weeks.

The bottom of my pool (under the liner) is a mixture of concrete and vermiculite, it is designed to allow ground water to permiate through it to prevent it from cracking due to hydrostatic pressure or lifting out of the ground. I have a dry well under the pool which is connected (normally valved out) to the main pool pump. When the liner lifts slightly I just valve it to waste and run the pump to pump the ground water out -- works great. I would suggest this highly for anyone that builds a pool in an area with a high water table.

I just noticed last week we have a bit of water under the liner, but we have a fairly low water table.

Can it be caused by a leak in the liner and pooling on the backside?