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 sewer smell during washing machine drain cycle
Author: rebotim (OH)

I recently connected a new washing machine to a new standpipe installation. It looks great. It works (drains water) great but doesn't smell so great.

When the washing machine isn't operating, all is well (there is also small half bath on the same vent system). No "sewer smells" from anything (the standpipe, nor the half bath) When the washing machine operates, I get the sewer smell (although I haven't been able to pinpoint(maybe my nose is bad) it coming from the top of the standpipe). Once the washer stops the smell goes away.

In the wall I have a 2" standpipe going into a trap which I then tie into the vent system, roughly 3' from the main stack. all 2" pvc. (4" stack, 1.5" vent)

x vent
x x
x x
x xxxxxxxxxxxxxxx
x x
x main stack

From reading other posts, I see that improper venting is the common culprit for a lingering smell after a wash cycle is done (trap getting sucked dry), but I didn't see any posts for what typically causes the smell to occur only during the wm cycle.

Any suggestions?

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 Re: sewer smell during washing machine drain cycle
Author: rebotim (OH)

ok, my "x" diagram didn't translate too well.

2"standpipe ~3'High into
2" trap
moving horizontally about 6"
I vent the line,
and then move horizontally again ~3 feet to the main stack.

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 Re: sewer smell during washing machine drain cycle
Author: oncall

I have seen one install like yours that had a similar odor. What I found was the stand pipe was filling during the pump cycle then clearing/syphoning the stand pipe and pulling the trap dry before overflowing. So, I was able to get to the trap under the floor and increase the trap size to 3" PVC which fixed the odor issue. I got lucky because I could get to the trap. Also, make sure your main trap isn't partially blocked in some way?...

Good luck, Gerry

Gerry in PA.

You can always do it right the second time.....free!

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