Hi all: I have 2 skimmers. Both have 2 holes. In one of them the 2nd hole is capped off from underneath. In the other one, the 2nd hole is capped off with a winterization plug. My question is — is that winterization plug glued in and that pipe goes to main drain? If so is the main drain doing nothing? No suction at all? Just there for code and the pump is only pulling water from the 2 skimmers?