Slow drain - new tub

[Smythers]

Hi,

Having an issue with a new bathtub installed - the drain is extremely slow.

Unfortunately, I don't have any pictures to share, but I've attached an accurate illustration found on the web. It's a standard 4pc bathroom.

When we renovated, we did complete gut and installed new fixtures all around. We replaced the water supply lines with new pex and they're working great.

We left the original drain/vent lines intact, they are as illustrated. Those drain lines for the tub and vanity are the correct 1½" diameter and they exit into the vertical 3" main vent/soil stack, which is all up to local code (Ontario).

The old tub didn't have any kind of trap on it when we took it out (definitely not code in my neck of the woods). I cut the drain from the old tub just after the connection from the tub drain kit to the drain line leading back to the stack and installed a p-trap after the tub-overflow drain as in the picture attached.

Problem:

When we fill the tub and open the drain, the water seems to just sit there. The drain is monumentally slow, but it does eventually seep out on it's own.

The vanity drains just fine, although there is now a gurgling that can be heard from the drain/overflow of the tub that wasn't there in the old bathroom.

No issues with the toilet.

What I've done:

- Checked for clogs - I definitely didn't leave a rag in there as I had to glue new abs tub drain kit and new p trap to the existing drain. All drains were cleaned with a rag, visually inspected and vacuumed out thoroughly before any installation was done to them.

- Swore.

- Snaked the drain to the stack, no issues. I used a cheap, 15' x ¼" manual "drain auger" with not much of an open-wound boring head on it. Snaked it all the way back to the stack (wasn't far, 8' - 10'). I'm thinking of renting a better cleaning tool to make sure the line really is clear.

- Checked the plug/stopper. We installed a push-pull type stopper. There's only 2 positions on it, opened and close. When opened, it's clear to see that there is a sizable gap that allows the water to exit the tub. You can see down into the drain.

- Swore a lot.

Is it possible that the drain line slope is wrong and I've lost the siphoning action at the main stack? Those original lines were secured and did not move during the reno. But maybe the new tub drain is low enough to negatively affect the slope?

How likely is it that it's a clogged vent/stack? Again, vent lines are original, didn't move them, they worked fine before. Vanity seems to vent fine, but the gurgling suggests that maybe it's taking it's venting from the bathtub overflow/drain...

Any thoughts or suggestions would be appreciated.

 

[Jadnashua]

That's one symptom of a double trap. Did you dig down to verify whether or not there was a trap there, or just assume that because you couldn't see one, there wasn't?

 

[Sponsor]

 

[Smythers]

Thanks for the reply

It's a 2nd story bathroom, so thankfully, no digging was involved.

We did a complete gut, right down to studs and joists, and we ripped off the old sub floor and replaced that as well. We had a complete view of the entire plumbing system in that bathroom and there's definitely no double trap on that line.

The plumbing is as shown in that diagram in my original post.

 

[hj]

In that case you have a real mystery, BUT, there has NEVER been a time when a trap was not required on a bathtub. It is NOT a "clogged vent stack" and if it is installed properly there is NO "siphoning action of the main vent", in fact something like that is what vents are supposed to PREVENT.

 

[Cacher_Chick]

It the pipe is clear, my vote would be for lack of pitch or reverse pitch on the line.

 

[hj]

That very seldom affects the "flow rate" of a bathtub.

 

[Smythers]

The only thing is, I tied in to the original drain lines... I never checked the pitch from end to end other than the casual glance to notice that, yes, the drain at the stack-end looks lower than where the drain will meet the tub.

I agree that the idea of the drain pitch is a very rare thing indeed. And I really don't want to have to correct that - but it wouldn't be the end of the world. It's my worst case scenario.

I also agree that it shouldn't be the vent stack, as there are no other drain issues at any other fixture in the entire house. It's just the tub.

I'm tackling it tomorrow. I'm going to:

#1. Snake out the drain line with a better auger to ensure it's not a clog. By the description of the symptoms, this seems to be the likely problem.

#2. Check the vent stack for clogs... because if I didn't check it, THAT would end up being the problem... that's how lucky I am.

if any of that doesn't work out, then:

#3. Reroute the drain, giving it a proper slope. If I'm reading this correctly, a 1½ diameter drain pipe gets ¼" drop for every 1' of length to a max of 3" over 12' of distance between the furthest fixture on the drain and the soil pipe (stack), and using long sweep 90° elbows or 2 - 45° for corners. Hopefully I've got that right so far.

Am I missing anything? Is there anything else I could be trying?

I appreciate all the comments, thanks

 

[Dj2]

Go ahead and do #1 on your list. We will be waiting for the conclusions.

 

[Reach4]

If you let the tub fill up, and have water going out of both the overflow and drain at the same time, can the drain keep up with the full blast cold running? If so, that would tend to indicate to me that the restriction is in the tub drain plug area rather than the downstream plumbing.

 

[Smythers]

So the results are in, and the winner is:

Clogged drain!

I snaked out the entire drain line in that washroom and then tested the tub. We had 1 gallon of water in there and it drained in ~14.35 seconds. The gurgling noise coming from the tub drain/overflow from when we emptied the vanity is gone too.

My best guess is that there was a hair ball in there from before the reno. During the reno, it's possible some sawdust, drywall compound, etc got down there and helped to restrict the flow. Using this better designed auger, I figure I was able to push that clog all the way back to the 3" stack where it will hopefully flow out to the sewer and not cause any problems.

That problem really did my head in. I felt I had snaked that drain out sufficiently the first time and eliminated clogs from the possibilities. Sometimes you just have to go back to step 1 and try everything all over again.

Thanks all for helping me through this. Much appreciated!

 

[Dj2]

No, actually the winner is you!

I'm glad your trouble is "down the drain", and thank you for being a good listener.