great forum, been lurking for a while. finally registered to see if i could get some help on a recent project. i had my basement finished ~15 yrs ago, had a liberty 1/3hp sewage pump installed in a pit for the basement bath that was added. that pump did great. i never had problems with it. i started getting worried about it being so old so i just replaced it before there was an issue. i upgraded to a liberty 1/2hp LE51A with a float. i didnt change anything else when i did the install except for install a new check valve because the other one was inside the pit. there is a vent pipe that comes up and ties into a toilet vent, the discharge comes up and ties into the main house drain. for some reason they didnt go up and back down so that it ties in from the top, instead it goes in from the side. not a big deal since its been that way for 15 yrs. heres my dilemna. for some odd reason the pump will run every 2-2.5 hrs when it rains. i started thinking it was either the check valve thats above the sump has failed allowing water from the rest of the house to fill the pit, BUT even if no water is used in the house, it still runs after 2.5 hours. i dont think its the check valve because i can hear the water hammer noise when it shuts. then i started thinking it was the septic tank backing up into the house when the ground gets saturated after a hard rain, but i opened the trap outside the house during the storm and theres no backup of water. then i started wondering if the vent system was getting water in it somehow and filling the pit that way. is it possible that rain could enter the roof vents(i have 3) and somehow fill the pit, it is the lowest point in the house. i highly doubt that THAT much rain fills the pit, that would be a lot of rainwater. i ran the shower, sink, and toilet and it appears that the sump is emptying correctly and with the right amount of water. i was worried the float switch was hung, maybe the pump shifted and the float is sitting up against the wall of the pit but i doubt it. this never happened before i changed the pump. nothing else changed with the system. water is getting into the pit someway when it rains. it doesnt do it when its sunny and dry outside.