We have an above ground pool installed maybe 5-6 years ago (we just bought the house). The liner is very wrinkled on the bottom and the bottom feels very uneven, like when you walk you can feel dips in the ground, some small (like width of finger) some larger (like heel of your foot). Do we need to be replacing the liner soon ie this swimming season or can we wait til next swimming season? and with all the dips, will they need to level the ground when we reinstall liner? is that expensive?