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Water from sink backs up in stack pipe.

5K views 5 replies 5 participants last post by  Marlin 
#1 ·
I removed my gross laundry tub and washing machine drain pipe that hangs in the tub and replaced them with a sink in a counter top, plumbed the sink and the washing machine into the existing 3" drain that the laundry tub was plumbed into. I put in two traps, one on the washer is lower than the one on the sink, then I put in an air stack on the straight pipe that goes into the drain. It didn't have an air vent before but i figured it would be a good idea with the washer outlet being placed into the waste pipe. When I fill the sink and let it go down the drain (with the washer not running) the water fills up the air stack until its even with the sink water and then they both seep down the drain over 1 minute or so. The laundry tub used to drain super fast, so I know that I screwed up something. Did I not make the two traps at different enough heights? The sink drain has to go through both traps to drain. The washer only goes through the low one.
 
#5 ·
Its hard to picture exactly what you have. You should have came out of the 3" with 3"x2" spigot then a 45 to get to the horizontal then a 2" wye with one branch going to the sink with its own drum trap and the other branch of the wye going to your laundry stand pipe with its own drum trap. You would obviously reduce to 1-1/2" coming out of the wye to accomodate the drum traps. With drum traps you should not need any venting.
 
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