I live in an old building that was originally a single family residence but long ago was converted into four units. The unit below mine has flooded probably 10 times in the last year. Our landlord is pretty unhelpful in most cases. A few times ago he came out and looked at the hot water heater and had it replaced. the hot water heater is in a small closet with a door to outside and walls shared with the flooding unit and the garage.
The time after that I went and looked in the hot water heater closet and the floor was wet but the hot water heater and the basin it sat in were dry. The water was coming from the wall between the water heater and the flooding unit. The last two times it has flooded a plumber was actually called. The plumber has said both times that the unit floods when we, on the floor above, clog our kitchen sink. I thought that was a major design flaw for our sink on the second floor clogging to flood her apartment but we got a new sink drain trap and have been very careful about food falling in the drain since then. That didn't stop the last time it flooded when we hadn't used the sink the whole day.
Today I woke early to take a shower and while the shower was heating up I got a text message from the tenant below that their unit was flooding again! Now I can't take a shower without flooding her apartment. I'm afraid the landlord will do nothing about this. The plumber has been called out twice in the span of a month and has done nothing but tell us not to put food down our sink. We told them the last time that it was not a problem with food going down our sink. Is there anything we can do to get the landlord to actually fix this plumbing issue?
Residence is in California.