hi.
i learned a lot about plumbing from this exercise. it's not something i'd looked into before...
the eel fixed the drain. but, for future reference, this is what happened:
- your sump pump is connected to outside
- your floor drain is connected to the sanitary.
- there was a partial blockage deep in the sanitary, meaning the floor drain was emptying the basement water very slowly. this caused the sump pump to be running all the time to compensate.
- so, when it rained the basement got full of water and that water blocked the sanitary completely, causing the slow flush, sink gurgles, etc. given enough of a dry spell, it would have come down on it's own through a combination of slow floor drainage and sump pump action, but it's of course better to clear the plug.
so, the systems are not entirely separate. your pump is pumping excess water to the street, but most of the rain water is in fact flowing through the floor drain and into the sanitary, and if you were to block that off your pump probably wouldn't be able to keep up.
so, in the future, if you see a slow toilet after the rain, it means your basement is slowly flooding due to a blocked sanitary.
j