Basement Bathroom Venting

[NYDIY]

Hello All,

I see this has been asked before, but seems like each case is specific to the respective poster. I am looking to add a new basement bathroom (sink, toilet, shower). My first question is regarding the whole house trap found in the basement (see images below for pretty accurate layout). The left vertical pipe is a main stack and the right penetrates the foundation wall and has a opening on the other side with a perforated cap. Through my research I have found that these are no longer installed and often replaced. I have owned the house for almost 2 years and never had an issue nor did I hear of anything from the previous owner, and it was built in 1988. Since I have opened up the slab nearby, it wouldn't be much work to extended and uncover the trap in which case would any recommend that I have a plumber replace it with a backwater valve? Let me know your thoughts.

Second, being the basement there is really no simple way to vent to the roof. It could be possible if absolutely necessary, but would require some extensive work & to do so. With that being said I was thinking of using an AAV which appears to be allowed per NYS plumbing code - "Individual, branch and circuit vents shall be permitted to terminate with a connection to an individual or branch-type air admittance valve in accordance with Section 918.3.1". Correct me if I am wrong, but I assumed there is no chance I can tie into the right 3" vent line that is existing since it does not reach the roof.

I found a great diagram on this website that I hope to follow. I was thinking I could add the AAV at the top of the 3 vent line junction as indicated, and use a sure-vent wall box so that it can draw air from within the bathroom. The 3" line will tie into the existing sewer line. Am I over simplifying the venting? Any guidance would be appreciated!

 

[Jeff H Young]

Im sure you cant vent your fixtures out that vent as well. I have no Idea if your code allows removal of the house trap . or why they required in 1988 and would now decide its un needed . But not many places have the house traps. backwater valve would be welcome in keeping sewage out of basement

 

[Sponsor]

 

[Reach4]

Are you saying there is no roof vent? If so, and since things are working, I would leave it as it is.

Or at least I would leave that vent thru the basement wall in place, in the absence of a roof vent. A house needs a real vent to relieve pressure.

If you put in a backwater valve, it should be "normally open". Use that as a search term. The sewage check valves with a hanging flapper always leak after being in service for a while.

Ideally, the sewage from the upper floors would not pass thru the backwater valve. I am not a plumber or other pro.

 

[NYDIY]

So there are 3 roof vents all together, just none remotely close to tie into (which I don’t think code allows for). As far as the house trap, I don’t want to mess with it if not needed but they do nothing to stop a sewage backup from the street side if that ever happened. It took me awhile to identify what the 2 clean-outs were so in that process I found a lot about how house traps are often replaced these days to either solve or prevent issues. I’m positive they can be removed in my area and not violate any codes. The normally open back water valve would be an ideal way to replace in my opinion. I plan to call local plumbers and see if they have opinions on replacing it.

Aside from that, my big concern is figuring an appropriate way to vent the new bathroom. If that can’t be done, then I likely won’t worry about the trap.

 

[Reach4]

You are not in NYC. So AAVs should be OK for venting. You do need for there to be at least one roof vent-- not all of the vents can be AAVs.

By feeding the upper floors downstream of the backwater valve, you can still use the upstairs plumbing, even tho the backwater valve has closed due to rising water.

 

[NYDIY]

You are not in NYC. So AAVs should be OK for venting. You do need for there to be at least one roof vent-- not all of the vents can be AAVs.

By feeding the upper floors downstream of the backwater valve, you can still use the upstairs plumbing, even tho the backwater valve has closed due to rising water.

Great so do you have any thoughts on the diagram I posted that showed the AAV at the top of the junction for the 3 vents? I realize there is probably a more economical way to do it, but I like the simplicity and access.