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knix98 01-01-2014 03:09 PM

Washer Drain Pipe
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My washer drain pipe keeps overflowing. I tried snaking it but a clog does not seem to be the problem. I think it may be the setup. If you look at the picture originally the standpipe was 9 inches (which was only slightly longer than the pipe leaving the trap) I thought this maybe be the problem so I extended the stand pipe by 24 inches, but this has not helped at all. Seems as if the water is getting stuck at the trap not sure though. Any suggestions? Thank you in advance!

inspectorD 01-02-2014 05:17 AM

Welcome a- board :D
It really looks like a trap,,, but it isn't. This is probably the issue. The water being forced into the standpipe, just cannot handle the volume.

Wuzzat? 01-02-2014 06:46 AM

Force hot water into the pipe for a solid minute. If the water comes out on your roof there may be a clog, probably from lint.
Repeat for the roof vent but with helpers in the house watching for overflows.

Fill your washer with a known quantity of water and then select the drain part of the cycle. Check how long it takes to empty.
This will give your gallons per minute flow rate and this number should be compared to the posted capacity of your (1-1/2" ID?) drain pipe.

nealtw 01-02-2014 07:40 AM

How far away from the stack is it?

bud16415 01-02-2014 09:00 AM

I have no clue on this but has all the markings of a DIY trap setup and most likely doesn’t have a stack in the line or if it tees into another line that stack is too far from the homemade trap to do any good.

Water will chug down a line like that but without being able to get air in behind it will never flow fast. Compare it to pouring from a gallon jug where the air coming in has to pass the water going out when you hold the jug straight down, now poke a hole in the bottom of the jug and try it with a vent hole to let the air in.

That homemade trap is fine and doing its job by keeping sewer gas from coming back. It’s also doing a second job of not letting air go down the line the water moving down pulls a vacuum on the line trying to suck the water out of the trap but new water keeps sealing it off. Thus the slow flow and acting like it’s kind of plugged.

knix98 01-02-2014 07:02 PM

I really don't know anything about plumbing so Im not sure where the stack is or if there is a stack. The drain pipe goes into the basement wall which is about 6-8 feet away but uses probably 10-12ft of pipe since it encompasses two walls. Somebody suggested that the trap was too deep so I cut it to make it shorter but that did not help the problem at all.

nealtw 01-02-2014 07:26 PM

The stack is a pipe that runs up to the main floor of the house to pick up other drains and continues thru the roof for a vent. Without a vent the water running down the pipe will vacumn the water out of the trap and allow sewr gas into the house like there was no trap. There is a limit to how long a run can be befor you have to add another pipe freom this one up and over to the stack so air can get behind the water and stop the vacumn. 12 ft would be way past that limit. Some set this up and likely made the oversize trap to help with that problem.
All this may be over simplified but now I hope you can have a look around and see what you have. You also want to check the slope of the pipe. Old a level up to the pipe and hold it level and see how far the pipe is off level. 1/2" with a 2 ft level would be 1/4" per foot slope.

Wuzzat? 01-03-2014 02:09 PM

That high vertical pipe should take care of level problems.

At this point I'd try to take a peek at a copy of the plumbing code at a tech bookstore. The plumbing code excerpts in my copy in the IRC 1999 are pretty detailed and pretty complicated. When I added a bathroom vanity I almost had to reroute the pipes in the wall.

The designers of the OP's system may have also run up against nasty problems and that system may represent their compromise; they did the best they could without tearing down walls. They gambled.

inspectorD 01-03-2014 03:40 PM

1 Attachment(s)
try this...

Wuzzat? 01-03-2014 04:23 PM


Originally Posted by inspectorD (Post 98009)
try this...

Yeah, that's kind of what I ran into. And IIRC that 4", 5" segment had a downslope.
The problem was the vanity sink was not exactly the same height as the original wall hanging sink.
And, since it was a three dimensional problem, locating the holes on the back wall of the vanity was beyond my two dimensional thinking.

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