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Deep trap

Posted by bus_driver (My Page) on
Sat, May 21, 11 at 12:52

A tract of modest houses near here were built about 1968 by the same builder. No-hub cast iron drains. The washer box is in the wall with 1 1/2" drain and concealed below it is an extremely deep cast iron trap with sharp bend at the bottom. It is not unusual for the washer to discharge water faster than the trap can handle it with the resulting minor overflow at the box. Even a 1/4 snake will not go through the trap due to the sharp bend at the bottom. Replacing with PVC seems to the best solution.
Other suggestions?


Follow-Up Postings:

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RE: Deep trap

I believe this is why washer standpipes are now required to be 2". I've always thought expanding soap foam was the culprit.
In a rental, I wrapped the washer drain hose with a 2" wide strip of old innertube rubber until it was a pressure fit into the standpipe. Some duct tape for extra security and it held for several years.


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RE: Deep trap

seeing images of P traps, i see they are all the same shape.
There is no "deep" trap option.
I think a normal shaped P trap of 1.5" diameter will still work well.

In Canada, the same washers work off 1.5" traps all the time. When US code got upgraded to require 2" pipe for showers and for washer standpipes, it was to allow longer distances so builders could make larger spaces. Otherwise a lot more venting had to be provided. My writing this out does not mean I know for a fact why a change in Code got voted by the committee; I'm surmising. Indulge me as I repeat the following factoid: in Canada, the exact same washing machines all work without backing up. Now, think about this. In Canada, is the distance of the 1.5" trap arm small enough to work right, or do Canadians just happen to put less soap in their soap trays? I really REALLY think that suds are not the obstacle to overcome.


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RE: Deep trap

Yes, deep traps do exist and were used in this tract of homes.

Here is a link that might be useful: Traps


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