Last week we had a clogged main. The main pipe access is down at the sump pit in the basement and the plumber couldn't open the caps (very old pipe, never opened before). Eventually he just drilled a hole on the cap to get the snake in and cleaned. After that, we just kind of use a plastic bag to cover the hole. Do I really need to seal the hole with something? I don't smell any odor from the hole and somehow I think it is a good idea to leave it like that because if the next time it backs up again, the water would come out from the hole which is in the pit which can hold probably 20-30 gals of water instead of backing up from the toilet in the basement like last time which made a mess... Or am I wrong? Thanks