When we first purchased our home and pulled back the cover of the pool, this is what we found:
It looked a little ominous, but the cover had a couple of rips in it and overall the vinyl appeared to be in good shape, just dirty. We swept and cleaned what we could and then started adding water.
A couple of things about vinyl pools (we didn't know anything about them before we had one):
WHAT IS A VINYL LINER POOL?
We thought it was vinyl covering concrete. Nope. Ours has a sand floor under the vinyl and fiberglass frame on the sides. The vinyl has a lip that goes into the frame to hold it in place.
NEVER EMPTY IT
You should NEVER empty them all of the way. Before winter, you drop the water level to just below the filter and leave the pool filled with water. If the pool is drained and left, the vinyl can pull away from the side or wrinkle up. If not covered, I've read they can even get brittle and break. We thought the previous owners had drained the pool, so we just cleaned it and started filling it.
WHAT IF THERE IS SOME WATER IN THE DEEP END?
If there is water in the deep end, but not the rest of the pool, there is a good chance there is a hole in the vinyl. It can be hard to know if there is a hole. We had no idea how long it would take to fill our 35,000ish gallon pool. We started filling ours... and filling it... and filling it for about 3 days before we said, wow, this isn't really filling up. We stopped filling, and it all drained in about 24 hours.
HOW LONG DOES IT TAKE TO FILL A POOL?
Our 35,000ish gallon pool takes a little over 24 hours to fill if the deep end is already about 1/2 full.
HOW TO FIND A LEAK
If there is some water in the deep end and you fill it a bit and have a leak, your hole is going to be about where the water was sitting when you first started. We filled ours a couple of inches, and then used red dye and squirted some slowly and watched the dye. We started with the seams, didn't find anything, so then moved on to the walls of the pool. When we found the hole, we were surprised it took us so long to find because it was a quarter-size hole. It looked like someone had shoved a pole down to see how deep it was and punched it right through the liner.
HOW TO PATCH A LEAK
There are cheap patch kits (under $6) for vinyl pools. We got ours at Walmart in the pool section. Just follow the directions. It was super easy to patch and quick.
From there, we added 2 packets of chlorine shock to kill the bugs and bacteria and filled the pool, which filled very quickly this time! We filled to 1/2 way up the skimmer (square hole), and added 4 more packets of chlorine shock. And we added another 1-2 chlorine tabs in each of the 2 skimmer baskets. Then we used the vaccuum hose on the "waste" setting on a sand filter to begin sucking up the muck from the deep end. It took us forever because our yard besides the pool is tiny, so we had to vaccuum for a bit, then stop and let it soak into the ground, vaccuum and let it soak, etc.
Once we had it relatively clean, we took a small jar of water to our local pool store, where they tested it (it was only about $12 to have it tested) and said the alkalinity was low. We added 12# bag of alkaline and a little more chlorine and began to swim!