Hello, My house has a 1000 liter slab water tank. The collector is in the ceiling, but has no drain key. I have to place a drain to be able to clean the tank and I discarded to put it in the collector for how cumbersome it would be to drain it in that place (a loft with no exit to the outside). I was reading and I saw that there are pieces that I can place by boring the tank, like flanges. I wanted to ask you: - Since the purpose is to clean the tank, should I drill it down? - Being a 1000 liter tank, how many inches should the drain be? - How should I seal it so that it doesn't lose later? Thank you very much for the help you can give me! Sincerely.