Bathtub drain too low, backing up when washer drains. What can I do?


Old 09-08-13, 02:45 PM
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Bathtub drain too low, backing up when washer drains. What can I do?

While running the clothes washer I've noticed that on the rinse cycle the bathtub drain backs up with some not so good smelling water and also seems to drain very slowly. Initially I thought this might be a clogged sewer main, but after inspection I noticed the bathroom drain has standing water inside almost coming into the tub itself. I was able to get access to the plumbing behind and noticed this arrangement. The blue line is the bathtub, red is the washer drain, and green is the bathroom sink. I'm not sure what the other pipe extending upward is marked "?".

It really seems that the bathtub drain sits too low to work correctly. Is there anything I can do about this other than raising the entire tub?
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Last edited by Temp08; 09-08-13 at 03:31 PM.
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Old 09-08-13, 08:22 PM
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If the tub is used for showers as well, there is hair clogging the pipes somewhere. That's guaranteed. Everyone else will say NO but I would put some Liquid Fire from Ace hardware in the bath drain or at least try to snake it.
Old 09-09-13, 04:24 AM
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Why is the bath drain sitting above grade? Is the tub elevated?
Old 09-09-13, 06:02 AM
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Yes, I will chime in and say do not use pour down the drain chemicals. If water is constantly standing high in the drain of the tub and does not go down I don't think it indicates a clog so much as an elevation problem. I hope the floor of your bathroom is about a foot higher than the room where you took the picture. Have you held a level up to the horizontal pipe run to see if it has fall?

The unknown vertical pipe is probably the vent for the plumbing. It should extend up and eventually out your roof.
Old 09-09-13, 10:25 AM
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Thanks Pilot Dane. I think you hit it with the horizontal pipe comment, it is sitting exactly level and is itself almost perfectly level with the drain opening in the bathtub (the tub is elevated ~6"). So I see now when a bunch of water gets dumped into that from the washer there is enough volume for long enough to start to run into the tub. I opened the wall more to the right to get access to the main (see the access plug in the picture) and it looks like there is enough space for me re-run the pipe with the correct grade.

However this would require me to cut more into those studs, and that makes me nervous. The previous owner already butchered the left most stud (you can see the horrible cutout in the center). I'm a little unsure how to proceed, but I think re-plumbing that horizontal pipe would solve my problem.
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