Washing machine overflowing-does the height of the AAV matter that much?

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Old 09-08-13, 04:29 PM
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Washing machine overflowing-does the height of the AAV matter that much?

I have a 2 inch PVC standpipe that goes to a p-trap 18 inches below. From the p-trap it goes into a tee where it drains to the bottom and vents to the top through a AAV(1 1/2"). The AAV is probably 3 to 4 inches above the flood point of the washer water box. Is it possible that those 2 inches short of the 6" code are causing the wahser to overflow? I can easily fix it but I want to make sure I get the root cause as this is a rental house and I do not want to keep trying to fix this.

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Old 09-08-13, 07:09 PM
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Does anything else drain into that pipe, besides that washer?
 
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Old 09-09-13, 03:00 AM
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No, the pipe runs about 20 feet under the house where it meets with one other 2" drain line then into 4" sewer line
 
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Old 09-09-13, 04:48 AM
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Did it ever work? if so you may have a clog.
 
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Old 09-09-13, 06:58 AM
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If the overflow were coming from the AAV, I'd say that the height might be the problem. But, even then, I'd think that it is more likely a clog.

If I recall my Oatey AAV material correctly, it only needs 4" to get enough back air pressure to close the valve and prevent sewer gasses. 6" would just be local code providing a decent safety margin.
 
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Old 09-09-13, 09:36 AM
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Yes and no. It had an illegal trap(was not really a trap at all) but it was also vented into the attic. I replace the piping with a p trap and AAV. I am starting to wonder if this is not a probelm with pipe geometry. Meaning that the trap and 90 degree going into the tee are causing sometype of flow restriction.
 
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Old 09-09-13, 10:17 AM
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You might want to increase the 18" to the upper range of 30 inches. This would supply more pressure to get past any blockage. Since nobody asked; are you sure the AAV is venting correctly?

It sounds like you have a similar issue with creative plumbing that I had. A washing machine was discharged into what I assume was a cut off vent for the main system. I was fortunate in that I had an energy efficient washing machine that didn't pump out nearly as much as a standard old model and the smaller pipe was able to handle it.

Another solution that you might be able to do is install a washroom sink for the washing machine to drain into.

Just to hit the legal side of this; do you have clearance from your landlord to do all this? Either your landlord should be doing this work or else the work shouldn't be done, since it destroys any sort of "it's been that way for a while, so we won't enforce the code now" kind view by the local code officer.
 
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Old 09-09-13, 12:45 PM
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I will try that....actually I am the landlord, I was not clear on that
 
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Old 09-11-13, 06:09 AM
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I would vote for a clog being the culprit. Venting is important, but I don't believe that the vent would be impeding the flow of drain water.

Extending the pipe up another 12" would provide more holding volume before it overflows, but won't specifically fix the problem. You said it drains 20' under the floor and meets up with another drain. What else drains into that?

I'd try snaking it first, but if it's a kitchen draining into the same 2" pipe, you may need a snake with a bigger head to push out the grease and gunk that's likely built up.
 
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