I'm having a problem with water backing up in both our front shower/tub and the shower in the back of the house. It seems to happen in front when the washer is going (also in front bathroom), we don't ever use the back shower so I don't know when it's happening, but I went back there yesterday and found standing water. Today it had drained about halfway. The front tub/shower drains somewhat slow but not that slow - it can drain fast enough to take a shower without filling up, but not much more than that. I have a concrete slab by the way. HELP!!

Are you on city sewer or a septic tank?