Drain gurgle/venting problem tub and shower

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khedrei

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Any advice would be appreciated.

Here is the new set up. It was all done with 1.5 inch ABS, which is the same as what was in there before. I was not able to upgrade to 2 inch without ripping out all kinds of walls downstairs. Everything is sloped properly.

Problem: If I fill the tub, and then drain it I get major gurgles from the shower drain. Seems to me that the pipe fills up completely and it is trying to suck air from the shower drain disturbing the water in the trap and making a loud noise. It also shakes the pipe down to the basement. There is no problem with the tub running, only if you fill it. Basically the drain can keep up with the water flow coming from the supply pipes, but not if the tub is filled. There is no issue with the shower draining.

The previous set up was almost the same but used a double wye fitting where the tub and shower connect. It was located in the middle of the room inside a shower wall. When I removed the old shower wall to have an open shower I moved the vent into the side wall of the room and reconnected it the same way in the attic to the existing vent.

Thoughts:

1. Could there be a blockage in the vent in the attic or at the roof. The tub and shower have not been used in 6 years. Would it be likely due to the lack of use that a bird or something made a nest or something made it's way in there?

2. Is there a way to slow down how quickly the tub drains? Is that a legitimate solution? I know it works because when I put my fingers in the drain to slow it down, the problem stops.

3. Everything is tiled now, so it's going to be very hard to redo anything aside from wrecking walls and ceiling underneath, but I welcome any suggestions.
 

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Cacher_Chick

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A 1-1/2" pipe will only wet vent on the horizontal for about 3' before the chances of breaking the vent increase dramatically. The wet vent section should be 2", or the fixture trap should have had it's own vent.
 

Terry

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Looks like you're stuck with that.
A shower should have had a 2" drain. And we never do two of anything on 1.5"
I would have vented the toilet and the shower seperately to prevent the fixture from above from siphoning water from the shower trap. The other thing I see happening sometimes, as the lines goo up, is water from the tub filling the shower pan with goo.

A 2" line is twice the area or volume of a 1.5" pipe.
With 2", you would have had a chance at wet venting. Not so with 1.5"
 

hj

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You are dealing with the Bernoulli Effect of the rapid tub flow going past the shower connection. That is causing a low pressure area sucking the water, and air through the shower drain. The vent does NOTHING to prevent it. The only solution is a vent between the shower trap and the horizontal drain. It being all 1 1/2" makes it worse because that increased the water's velocity.
 

khedrei

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Thanks for all the advice. Terry, It was all done originally with 1.5" with both fixtures hooked up. I guess two lines on one drain was in the code back then? I know a plumber I hired tied my washing machine stand pipe into the same drain as my bathroom vanity on the same wall on a wet vent. But I guess the sink drains down right away with a T rather than a horizontal like this.

So even though the drain is 1.5" down to the basement, I could have still benefitted from 2" on the horizontal? Even if it went right back to 1.5?

Is slowing down the drain of the tub a legitimate solution? Is there a pop up drain plug that can do that, or would I have to jimmy something?
 

Terry

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You can't go from 1.5" to 2"

Because it was plumbed that way didn't make whoever did it smart, or right. There are plenty of dumb things being done.
What we are saying, is even with undersized piping, there is at least a better way than the way yours was done. There could have been improvements, even though someone stuck you with undersized pipes.

Wet venting is never allowed with 1.5" pipe.
Washers are not considerd for wet venting. They pump out far too much for that to work.
 

NHmaster3015

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Welllllllll actually under the IPC wet venting is now allowed with 1-1/2" and in fact you can vent two entire bathroom groups with 1-1/2" but that's IPC and Canada has its own set of rules. HJ may be right but I'd be more inclined to think that the problem is a blockage, rise or sag in the drain pipe. At any rate though, the vent has nothing to do with the problem.
 

hj

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quote; 'd be more inclined to think that the problem is a blockage, rise or sag in the drain pipe.

Your inclination is wrong. in fact a blockage, sag, or rise might solve the problem even though it would create different ones.
 

khedrei

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Thanks Terry and everyone else. I appreciate the tips for the future so I know how to fix things. Is anyone able to answer whether closing off the drain somewhat to slow down the tub drain is a good way to solve this. Aside from doing a major demo of course. It's a stand alone tub so there isn't exactly a rush to drain it. As I said the shower drains just fine.
 

hboogz

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You are dealing with the Bernoulli Effect of the rapid tub flow going past the shower connection. That is causing a low pressure area sucking the water, and air through the shower drain. The vent does NOTHING to prevent it. The only solution is a vent between the shower trap and the horizontal drain. It being all 1 1/2" makes it worse because that increased the water's velocity.

Just trying to get some clarity. In the event this was done with 2", what would the proper way to wet vent? I'm new at this, so forgive me, but would you need to a wye between the shower and the, what i presume is the lav (45 wye) connected on same horizontal? and branch that into the vent stack using a T at the vent stack ?
 

khedrei

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Just to clarify, the sinks are not connected to this branch of 1.5. They're on the other side of the washroom. They may connect tto the same 3 inch in the basement or in the wall but this branch of 1.5 that I pictured is just the tub and shower.

Hj is there a way to slow down the drain? What do you think of that idea.
 

Cacher_Chick

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No plumber is going to suggest that you do something to "slow down" the drain.

Sometimes we have to push the "reset" button and do things over. When everything is done right, everything works the way it should, and it will be a lesson learned for any projects we might tackle in the future.
 

hboogz

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IF it were 2", then the pipe area would be large enough to allow air flow along with the water and it would not happen.

Thanks HJ. So the layout and the fittings/connectors are all correct (assuming pitch is right). If this was all 2" then nothing in the drawing would change for it to properly wet vent? Got it.
 
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