I am about to replace the liner on my pool, because of a need to replace a leaking skimmer. I removed the return fitting and started to remove the liner and the hole in the aluminum wall where the return fits is starting to corrode. The return fitting was attached to the wall with 4 screws going through the wall and into the back piece of the fitting. The holes that the screws were in were completely corroded and now are a part of the return hole itself making the return hole slightly larger and is not circular in shape anymore. The new fitting that I got with the widemouth skimmer is slightly larger and attaches through the wall with a nut on the outside of the wall.
I was thinking I could just smooth the edges and use the same hole, but was thinking that it may be weak to far out and eventually fall apart where the fitting would only be held by the liner.
But then I was thinking I should cut a piece of metal to put on the inside of the wall to reinforce the hole the skimmer goes through. Cut a hole in the center of it, match it up with the existing hole and pop rivet it together. I had a couple questions about that. How large should the piece of metal be? I need a 2 3/8 inch hole for the return fitting. The hole in the wall now is only weak on the very edge of the hole, so it is good metal out about 1" from the edges of the hole. Would a 6"x6" patch be large enough or should I make it larger? 8"? 12"? or even larger? What material should the metal be? I was looking at aluminum at home depot but they only have 6X18 in a decent thickness aluminum and thinner aluminum in larger sizes. I also have about a 12" piece of stainless steel laying around but that would be harder to cut a perfect hole... Does the hole need cut perfectly circular? If I do put a piece of metal on the inside should I cut the existing hole larger so the fitting only goes through one layer of metal or just leave it so it goes through both layers of metal?
The hole around the skimmer I am going to cut larger to switch to a widemouth skimmer so I should be fine there. But I had a skimmer that slid in from the top of the wall so when I install the skimmer three of the middle top face plate screws will only be going through the liner and gasket (no metal wall). Will that be fine or should I patch and recut that hole also?