I am replacing/upgrading the shower in the basement (i.e. - concrete slab) and have removed the existing fiberglass shower enclosure and found that all of the floor level wood and drywall is severely rotted. I noticed that when the washing machine runs, which is also on the basement slab floor level, gray water is coming back up through the drain and flooding (minorly) the floor in the vicinity of the shower drain. I presume this is an existing condition because of the rot.

I would like to fix this if possible before installing the tile shower and base.

Any idea how I might do that?

Thanks in advance
--Duncan

Duncan, just a few questions before I can offer any real advice so bear with me. The washer drain line needs to be at least a 2" pipe,not just the hose. Do you know the size of your drain pipe? The drain line is backing up either due to blockage or being undersized. As you might guess, one will be easier than the other to fix. Back to you

Thanks for the quick response. The washing machine drain fortunately is 2" so should be good there. Presumably next step is to auger the line as there is potential blockage.

--Duncan

Your are correct, if the pipe is 2" and it is backing into the shower there needs to be some augering. The shower is trapped so it might be hard to get a 1/2 snake through there. Is there a clean out close by up stream or can you snake down the washer stand pipe? Only trouble with the stand pipe is if it is a Tee at the drain pipe connection instead of a Wye the rod could go the wrong way or get stuck.

I've done some further investigation and am baffled.

I confirmed that the shower drain only leaks when the washing machine runs.

To test the drainage, I put a garden hose in the washing machine drain standpipe and turned it on full bore for about 20 minutes. There was no leaking in the shower and the drain kept up with the flow with seemingly no problem.

The only thing I can think of is that the water coming out of the washing machine contains 'gray' water or perhaps soapy water.

Any ideas?

A garden hose running full blast is still not the volume a washer puts out when it pumps to the drain. The newer Maytags pump so much water that the 2009 plumbing code will up the pipe to 3". When you say the shwer leaked do you mean gray water came up out of the drain or is the drain actually leaking around a connection?

The water that is leaking around the shower drain looks clean (not soapy or murky). Frankly I'm not sure yet if the water is leaking right out of the drain or from somewhere below as I have just seen the results after coming home from work. I'll run the washing machine myself soon and see if I can see where it is coming out of.

If I were to replace with 3", how far back would I need to go? Presume all the way to the main line.

You are correct, the 3" drain would need to stay 3" all of the way to your main drain line which is likely 4". I am not suggesting tearing out the old 2" line. We will probably end up rodding your drains rather than replumbing.