We just remodeled a 1st floor bathroom. There is 1 sink, a shower and a toilet. They all drain into a 4" main with the shower at the far end then the sink then the shower. Before remodeling there were 2, 2" vents tapped off the horizontal main, 1 between the toilet and the sink drain entry and one between the shower and sink entry. Those 2 were tied together and tied into the 1 1/2 vent off the sink. That in turn went up and tied into a 4" vent stack that was tied into the main between the shower and sink. Confused? In the remodel a plummer told us we could eliminate the 4" cast vent that ran up and that the 2 2" vents would suffice. So we did. After it was finished all worked well for a couple of months then sometimes when the shower drained, it would set up a siphon actions and pull the water out of the toilet. I had installed a clean-out at the end of the line after the toilet, and I could unscrew that plug and air would suck in and all would work fine. To test my therory I tapped off the clean out and ran another 2 " vent. It seems to be OK now. Is there any promlem with letting this vent at the end of the line?

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Originally Posted by reds2005

We just remodeled a 1st floor bathroom. There is 1 sink, a shower and a toilet. They all drain into a 4" main with the shower at the far end then the sink then the shower. Before remodeling there were 2, 2" vents tapped off of the horizontal main, 1 between the toilet and the sink drain entry and one between the shower and sink entry. Those 2 were tied together and tied into the 1 1/2 vent off of the sink. That in turn went up and tied into a 4" vent stack that was tied into the main between the shower and sink. Confused? In the remodel a plummer told us we could eliminate the 4" cast vent that ran up and that the 2 2" vents would suffice. So we did. After it was finished all worked well for a couple of months then sometimes when the shower drained, it would set up a siphon actions and pull the water out of the toilet. I had installed a clean-out at the end of the line after the toilet, and I could unscrew that plug and air would suck in and all would work fine. To test my therory I tapped off the clean out and ran another 2 " vent. It seems to be ok now. Is there any promlem with letting this vent at the end of the line?

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What happened to the 1 1/2" lavatory vent? What now vents it? Where did you terminate the vent that you took off the clean out? All this could have been eliminated if the plumber had increased the lavatory vent to 2" and discharged the shower into the lavatory drain providing the lavatory discharged downstream from the toilet. Was this a licensed plumber that did the work? Regards, Tom

I guess I wasn't clear in my description. Here is the order of drainage from the end of the line. Clean-out, toilet, 4' of 4", 2" vent, sink drain, 2" vent, shower drain, then out to the main sewer drain. The 2, 2" vents tie together and then tie into the 1 1/2" vent that comes off of the sink between the trap and where it ties into the main drain and then it goes up and terminates through a 4" roof vent. I put the new vent in at the clean-uot which is actually the end of the line and terminated it at the roof.

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Originally Posted by reds2005

I guess I wasn't clear in my description. Here is the order of drainage from the end of the line. Clean-out, toilet, 4' of 4", 2" vent, sink drain, 2" vent, shower drain, then out to the main sewer drain. The 2, 2" vents tie together and then tie into the 1 1/2" vent that comes off of the sink between the trap and where it ties into the main drain and then it goes up and terminates through a 4" roof vent. I put the new vent in at the clean-uot which is actually the end of the line and terminated it at the roof.

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Thanks for the clarification. Your vent layout works for me. Tom

Ok, no gurgle or siphon action now. Now when the shower runs a long time it starts to back up and drain very slowly. The toilet then bubbles up and sewer gas is present. If the shower is allowed to drain, all else work fine after short time. We've had problems with roots in the sewer pipe before and we haven't had them snaked for a while. This sounds more to me like a partial block to me because it is bubbling up not gurggling down. What do you think?

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Originally Posted by reds2005

Ok, no gurgle or siphon action now. Now when the shower runs a long time it starts to back up and drain very slowly. The toilet then bubbles up and sewer gas is present. If the shower is allowed to drain, all else work fine after short time. We've had problems with roots in the sewer pipe before and we haven't had them snaked for a while. This sounds more to me like a partial block to me because it is bubbling up not gurggling down. What do you think?

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I think you're correct. You have a partial blockage in your line. Good luck, Tom