Hi,

We are renovating our upstairs bathroom. Originally it had just a whirlpool tub, and now it has the same tub plus a separate shower beside it. We're testing the plumbing to make sure everything works before closing up the walls (& the ceiling below).

The bathtub and shower connect to the same the same drain pipe, down-line from their own individual P-traps.

When we fill up the tub and then pull the plug out, some water comes up in the shower drain and spills into the shower floor - then it drains out again. When we described the problem to someone at the local big-box home improvement store, they suggested putting an in-line vent between the shower P-trap and the y-joint where the shower drain water meets the shared drain. We did so, but the problem is still there.

Is there something like a one-way valve we can install? Or is there something else we can do? Any suggestions, advice or a point in the right direction would be hugely appreciated! Thanks in advance,

Shannon

Hi Shannon,

Sounds like you may have a partial blockage downstream from the shower. Before I did any thing I would snake out the drain lines.

"When we described the problem to someone at the local big-box home improvement store, they suggested putting an in-line vent between the shower P-trap and the y-joint where the shower drain water meets the shared drain. We did so, but the problem is still there."
A vent problem would cause the fixtures to drain slow and you would hear a "gurgle" from the traps. Clogs cause back ups not vents. But I guess that's why they work at a "big box store" instead of out in the field doing plumbing. Snake out the drain lines and if you haven't put back fall on your installation your problem should be fixed. Regards, Tom

Hi Tom,

Thanks for your fast response! It gave us some much-appreciated hope at the end of a frustrating home-reno day. I just got a call from my house-mate, who's taken a day off work today to deal with some home reno issues such as this plumbing (fun stuff!). He snaked the drain all the way to the main stack - almost the entire snake was in the pipes, save for a couple of feet. He didn't see or feel evidence of a clog though, and upon filling & emptying the bathtub afterwards saw that the water is still coming up in the shower drain.

To me it makes sense that some water would emerge in the shower, as the level of the water in the bathtub when it's full is much higher than the shower floor - but I'm a plumbing newbie and don't have a good intuition about how these things work.

I wanted to ask you as well, about your comment that "if you haven't put back fall on your installation your problem should be fixed" What is back fall?

If we should call in a pro, we will - in your opinion, is there anything else we should be looking at first? Thanks again,

Shannon
Gatineau, Quebec, Canada

Hi Shannon,

"To me it makes sense that some water would emerge in the shower, as the level of the water in the bathtub when it's full is much higher than the shower floor - but I'm a plumbing newbie and don't have a good intuition about how these things work."

For a "newbie" your intuition's working just fine in my book. Since water will seek its own level it makes perfectly good sense. However unless the drain pipes are undersized or there's a partial clog in the drainage line the flow will drain right past the connection to the shower. The configuration of the fittings see to that. What did your companion use for a snake and where did he snake from? What ever's in there's still there. Your boy missed it. Perhaps the snake was too small and he just pushed through the clog or he snaked from the wrong spot but there's no doubt he missed it. Answer me and I'll get right back to you. Tom

Hi Tom,

The snake was one we bought at the big-box store a couple of years ago - it's just a long metal coil with a sleeve-type handle & tightening screw at one end. The "business end" of the snake is probably a little less than 1" in diameter.

He snaked from the shower drain, as the bath drain was too hard to try to take apart. The snake went from the shower drain past the y-joint where it merges with the bath drain flow, over to the toilet & main stack.

I think the drain pipes are standard-sized - 1.5" diameter, if I'm not mistaken. I can take a picture tonight if that would help. What might help more is if I get him to describe in his own words what he's done.

In the meantime, thanks for the advice and moral support - much apprec.
Shannon

Hey Shannon.

"I think the drain pipes are standard-sized - 1.5" diameter"

The average size for tub and shower drains are 2". But if the tub drained Ok and then the shower begans to back up then there is a partial clog that's making the discharge back up. The line has to be blocked there just isn't any explanation. Cheers, Tom

Hi Tom,
Just wanted to let you know that we got it fixed. We snaked the whole thing twice but no improvement, so called in a plumber - he suggested we re-route the plumbing so the shower and bathtub each go directly to the main stack, instead of merging upstream of the stack. Then he stayed around and helped us, as we were fed up by that point. Everything now drains like a charm. Total damage was around $305, which is $261 or so in your dollars... could've been worse!

I'm confident there was a partial clog as you suggested; we just weren't hitting it. Thanks again for the advice - much appreciated!! Reading through this forum has been very educational for me.

Regards,
Shannon