Hi, So I took a 3 month plumbing course so I only know the very basics. This problem I have is a bit confusing though. So recently it seems one of my drains in the basement backed up (the one in the laundry room) but not too much water backed up. Anyway, I checked my other floor drains and the clean-out located at the building entrance and the water level is unusually high (almost at floor level). There are also lots of particles in each of the drain. Anyway so I figured since all of them are like this, the block would have to be anywhere from the building entrance cleanout to the city main. So here's the weird part. My uncle who I'm living with decided to put hot water down one of the drains (farthest from the building entrance) and I thought it was going to overflow and it really should have, but it didn't! No matter how much water you put down that drain the water level stayed the same. This would mean the water is definitely going somewhere and there is no blockage which leaves me in even more confusion. (I wanted to try to see if the other drains and cleanout had this same weird phenomenon but my uncle decided to put enzymes down all the drains and told me not to put any water down.) So what's going on? I'm very confused. Is there a block or isn't there? The water level in all the drains suggest there is, but the fact that there is no overflow suggests there isn't. So I didn't know where to start to solve this problem so I decided to put down all the things that I knew was absolutely true. I left out assumptions or anything that wasn't 100%. 1. The water level is unusually high in all drains 2. Water backed up in 1 of the drains (the one in the laundry room) 3. Adding water to one of the drains (the one farthest from the building entrance) does not result in overflow. Water level stays the same regardless of how much water you add. 4. Unknown particles can be seen in the water of all three drains. Help from a professional or experienced person in this sector would greatly be appreciated. This house was built in the 1950s-1960s so the plumbing system might be different from what I learned and from today's standard. Thank you very much