I am installing a pool and I was wondering what is a safe weed killer for under the liner? I've heard of pure blue but I don't think you can get that in Canada. I've also heard about people using round up and I don't know how safe that would be with the liner. I searched and heard of people using salt, vinegar and bleach but do they or anything else last long term? I have removed all grass, and thought all the roots and set up the walls with the sand that is level.
I have been trying to use the old liner since I was given the pool but it appears to have shrunk too much so I bought a new one. But during my 3 failed attempts to get the liner to match up properly I have noticed weeds growing through the sand and it doesn't appear that being covered by the liner stopped them one bit and they continue to grow. The weeds look like a climbing weed vine thing. So currently I have the walls set up with sand and Styrofoam coving.