If you are losing more than an inch or two of water every week in your above ground swimming pool, then you most likely have a leak somewhere in the pool. The first place to check when you have a leak in your swimming pool is in the plumbing pieces. Let the water level leak out until it reaches the bottom of the skimmer box and/or the return jet. If the water level stops at any of these points, then the problem lies there. If the water goes significantly below those points, then the leak is in the swimming pool liner.
If the leak is in the skimmer or return, then you will first want to tighten those components to make sure that they are tight on the pool wall. If there is still a problem, then you will have to replace that part. When you replace this part, also replace the gaskets that go with it. These should be new so that it can be secured to the swimming pool liner.
If the leak is in the swimming pool liner, then you will have to find the leak. If you see water seeping at one end of the pool, it does not necessarily mean the hole is near that end of the pool. Gravity could be taking that water to that side of the pool just because it may be the lowest part of the pool. The real only way you can find a hole is looking in the pool with goggles. Absolutely DO NOT drain the water out of an above ground pool!!!!! This will ruin the liner and you will have to replace it then. There may be some tools being sold in pool stores that will ‘detect’ a hole in your liner, but they rarely work, so your best bet is to look manually. Finally, you will want to find an adhesive that will let you patch the pool under water. Many patch kits sold in pool stores do not work, and some even ruin the liner. So when purchasing your adhesive, make sure you are getting something professional, or just find someone local that will patch the hole and stand by his/her work.