Our laundry room is in the basement and there is a utility sink in the laundry room and a sink on the other side of the wall in the bathroom. The stack is the upstairs kitchen sink, then the washing machine and then the 2 sinks in the basement bathroom and laundry room. When the washing machine drains, water backs up into both sinks. It has done this ever since we lived here but we recently did some remodeling and added additional riser pipes to increase the ventilation but this did not help. Is there any type of anti back flow valves that can be put in the sink drain traps to stop this problem?

 

The water that comes out of the washer is soapy at times and not like regular potable water. The dran line is probably all caked up with "stuff' and when the water from the washer drains it bubbles up from taveling through the rough pipes and can't drain fast enough to not come up the traps and into the sinks. I would have the pipes in the basement cleaned.

I assume all the plumbing is done right and the piping is sized and pitched correctly.

 

If there were and you installed them you'd have a mess in the laundry room. it's simple physics. water from the washer has to go somewhere. right now it's backing up into the sinks because it can't drain fast enough. if you block off the sinks it will just back up somewhere else - probably the laundry room but who knows?

I really suspect a flow restriction in your drain at some point beyond where the sinks and washer drains tie together. Washers dump a lot of water into the drain quickly when their pump kicks in - if there's any restriction you'll notice it even though you might not see an obvious problem with the sink drains.

-art-