Seeking Solutions

The cat pissed on the couch last night. The previous two nights, he pissed on our roommate's chair, which is now outside waiting to be taken away with the garbage (the big ass chair, Russia, as it was named by me). We are seeking solutions to this problem since at this point I'm worried he'll piss on my couch, and we are not sure that we can keep the other couch, depending on whether we can get the stench out. I just don't know if it will happen. We can't take the couch apart to clean it, so it's a 50-50 chance.

The obvious solutions are likely not going to work. It's not fair, we think, to get rid of the cat since he's been living in upheaval since the arrival of the other two cats. It would be hard to ask our roommate to get rid of her cat (only one is a problem), especially since it's not our house. The only other two things we can think of are (a) to get a new liter box and throw it and the cat into the basement at night and (b) to get plastic to cover the couches each night. Both of these options would incur a cost, and we are getting tired of putting money into a cat situation that hasn't been a problem before. Plus, these aren't our cats. The extensive air filtering system we now have - a bunch of little ones and an enormous one - are enough, we think. In fact, I'm going to have to buy more air sanitizer thingies soon.

The vacuuming and air sanitizers help a lot, but obviously do not address this problem of the cat pissing on the furniture. Anyone have any other ideas???