I have a problem with the washing machine overflowing from drain pipe. I am replacing the drain pipe because it is only 1 1/2in and 15in high. I need to know if I need to put a vent pipe in before p-trap? This hooks up to my sewer pipe that is about 1ft away!

Hi ZMAN:

It is a good idea, at a minimum to install a mechanical vent (AAV)..see images. It can be installed on the vertical or the horizontal. The AAV screws into a female threaded adapter. If no vent the trap can siphon and allow gasses into the home every time anything from above passes the washing machine fitting.

Lastly, 1.5" should work here...if it isn't working then I have to figure that the pipe has gotten choked down and is clogging up. Is this galvanized pipe into cast iron pipe? If so, the dissimilar metals can cause an electrolytic effect that can cause minerals to deposit and clog the pipe....let me know. This would require you to remove the pipe back to the main and chisel out the deposits to fix this best.

The 1.5" standpipe should be increased to 30 inches.

MARK

No pipe is pvc.

Install the vent and increase the standpipe to 30"... should fix this.

Otherwise, I need to figure the drain line it attaches to is clogging up..?

Thank You!

Quote:

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Originally Posted by zman23

I need to know if i need to put a vent pipe in before p-trap? !

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Mark answered this question with his pictures. Do not install a vent before trap, install after trap,(as mark has shown). Do as he says and you should be all set. Keep in mind that your drain may be plugged(as Mark also mentioned), so increasing size and height of standpipe may not cure your problem. I think I would start by augering the washer drain. Good luck and please let us know how things work out. Lee

I have already ran a auger through drain several times and found no obstructions. I then ran the washer on small load cycle and it did not back up!

What happens if you run a large load?

Did you extend the standpipe?

Let us know...

Thanks.

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I increased standpipe and installed mechanical vent (aav). Everything working great thank you!

Awesome news!

Thanks.