Will 24" standing 2" PVC pipe with p-trap also 2", following horizontal 8-9" pipe 2" diameter that goes into 1.5" horizontal pipe 6-7" long that tees into 3" stack be enough to pass water at discharge rate is 4.23 gal/min? On the horizontal part there is a wye 2" and 1.5" branch to drain bathroom sink. Currently there is 1.5" bathroom sink horizontal drain that tees into 3" stack. House is old, PVC is all yellow and I don't want to cut stack to add 2" for both washing and bathroom drain. There is no room to add a separate line for washing machine. Below bathroom sink tee on the stack there is kitchen sink tee that is also 1.5" branch. Washing machine usual water capacity is 6.8 gallons.

  • It can take the water the issue is can it VENT the air fast enough that will be trapped in the line and it gets worse dropping to 1.5 and those horizontal pieces. It will be one big air bubble that needs to burp. If I was in a jam like that I'd run the washer and try it - BUT i would have a 2 5-gallon buckets next to the washer in case I needed to drain somewhere and the drain failed. Best answer I can give with out looking at the convoluted piping. – user1946891 Jul 8 at 21:53
  • The 3" pipe is vented. By code from p-trap to the vent max distance is 5 ft. In this case it's 2 ft or less. As I said, currently there is 1.5" about 20" long drain from the bathroom sink. I think about extending it a bit by replacing 1.5" pipe with 2" as close to 3" vented pipe as I can, put wye to drain bathroom sink and p-trap with about 2 ft standpipe that is 2". I'd like to know if such combination will drain the washing machine Haier washer-dryer combo. The machine is very small. – yurinomusume Jul 9 at 1:00

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