Have a clogged, takes hours to empty bacj-up from slop sink, main 4" drain. At trap tried to remove street side bang-in plug but noticed water seeping out around edges so I'm figuring the blockage is on the street side. Or is this normal when uncorking street side? The 3" of water backed up in slop sink does go all the way down, so I figured the blockage to be in the trap or oon the house side of it. Ideas?