Bathtub drain and vent questions

[Karl Knudson]

I have a claw foot tub that I am trying to connect to my main drain stack. The old plumbing was a mess and not up to code but actually worked ok. My inspector said that he would tell me how to fix this mess but that was a few years when I added a different bathroom and remodeled a kitchen. I need some help from someone smarter than myself. I realized that my original idea created an S trap and I had not considered venting issues at all, so back to the drawing board. I am attaching a couple of photos. The stack is 4"XH. In the top of first photo the top connection is a 4" T that goes about 12" to the closet flange elbow, the next is a 2" Y for my tub drain that still has a bunch of old pipe connected to it that will go away, and below that is the 3" Y that serves other part of the house. From the bottom of the sub floor it is about a 21" drop to the 2" Y. Also it is about 25" horizontally from where the tub drain will come through the floor and connect to the 2" Y. How can I make this connection that will work well and meet code requirements for venting? Please let me know what other information would be useful. Thanks.

 

[Terry]

You should have a p-trap for the bathtub that is vented.
Normally that could tie back in at 42" above the floor to the other vent. In a work around, you could install an AAV for that purpose.

The vent would come off the horizontal tray arm on the top.
You can't see the vent here, it's out of the picture to the left.

 

[Sponsor]

 

[Karl Knudson]

My understanding is that those vents are acceptable some place and not others, how could I find out for my location? Also, I was looking at more options and thought I had one but it seems like a bad option. 10.5 feet away across the joists is my 2" vent that I had left for a future basement 1/2 bath but I may have found a better option. On the back side of the 4" T that connects to the closet elbow in the top of the picture has a 2" fitting plugged off. One of my concerns is how much I can drop from the drain to the trap and how that might effect operation. My vent would need to be above the trap to function at all. I think I read somewhere in this forum a 24" drop or less was ok but might get noisy. The total drop from the tub to the Y would be about 24". Also, the trap setup that i had purchased was expensive. I'm thinking maybe I could replace it with a less expensive PVC option since it will be below the floor now.

 

[Karl Knudson]

I'm guessing that my "better" option in the picture might not meet code either because it would not tie into the stack above the 42" level you had indicated. Tying into the other stack would not have that same issue. The question with that would be if I could drop that below the 2x10 floor joists or drill through to gain the height?

 

[Terry]

Cast cam be cut can coupled to, or the lead in the hub can be removed and using a donut new pipe installed. Those are 2" hubs.
A long tail piece is not the best option going into the p-trap. I prefer something shorter. I can't see your layout there to get a full idea of what you're up against. Is this being inspected? If so, you need to please your local inspector. A call to him would answer those questions. Where I'm plumbing, the AAV would be okay for venting. My preference is to always vent with piping, as it's a forever thing that doesn't need replacement later.

 

[Karl Knudson]

It is not being inspected as my permit is no longer active. This was existing and still in use when they inspected all of the new work for my kitchen and other bathroom. I tried to make some scale drawings and a couple of additional photos to try to help make sense out of my conundrum. In the first picture the drain will drop in between the 2 copper pipes in the upper left above the light in it's temporary location and connect to the 2" Y in the stack that still has the old mess attached. The other photos are for reference.

 

[Karl Knudson]

I thought I would try to to create some scale drawings that would illustrate some of my connection options for feedback. I also shared my temp;ate for reference. Please let me know what you think would be the best or if you see another solution. Thanks

 

[Karl Knudson]

I could still use some help finding a solution, I'm stuck on the whole project until I can get this figured out. I'm sure it would be apparent to any experienced plumber but I am not that. I'm a good enough plumber to do whatever needs to be done but not good enough to know what that is. I converted the pdf files to jpg files thinking that might work better. My option drawings are elevation for a concept of what is possible. I would still have questions about sizing and correct fittings and if the portion that I believe would be a wet vent would be acceptable or not. When I was looking for more info I did find my inspector and sent him an email as well. I could use some opinions on this style trap as well. I would appreciate any additional feedback that you might offer. Thanks

 

[Terry]

The drain for a tub includes a p-trap attached to a trap arm with 2% grade.
1/4" per foot grade.
No elbows going up or down to change that. Otherwise any venting you're doing is useless and the trap siphons.
The reason for the vent, is to break a siphon which can suck the trap dry.

 

[Karl Knudson]

Ok, that makes sense, that why S traps are bad. The drain portion seems to make sense, but the venting has a couple of options. I made two option drawings that should work and break the siphon. The drop to the trap would be about 12" from the tub and the horizontal portion would be approximately 13". The big question remaining is if I can connect to the 4" stack or I need to drill through the joists and connect to the other 2" vent. The 2" vent would meet the 42" above the floor requirement but the 4" stack connection would not. Please let me know which way you think is best and which vent connection is required and if my sizing is not correct. Thanks

 

[Karl Knudson]

So after reading a plumbing book and thinking about this way too much I think I have arrived at a solution. When Terry mentioned breaking the siphon it got me to think back to what is the reason why you would do something, what's the point. The reason that you want to tie a vent into the stack at 42" is to be above flood level so if there is a backup it will not flood the vent. I had resolved to remove the insulation and drill through all of the joist to go to the 2" vent until I realized by looking in my plumbing book that the horizontal leg of any vent is supposed to be well above flood level to start with. My next thought was what would happen if there was a backup and that vent flooded and my realization was that all of the basement fixtures connected to that vent would be flooded in the bathroom and laundry room becoming a potential for disaster. So my best solution is to connect all of the basement fixtures to the 2" vent and isolate the tub drain from the basement fixtures and connect the vent to the 4" stack by itself in case there ever was a backup it would not be able to flood the basement, the flooded vent would backup into the 4" stack. I don't think I have an option that would actually meet code but what I am replacing is an S trap without any venting so this will be much better that that. Thanks for your help. Any feedback would be appreciated.

 

[James Henry]

If your vent was tied in below the flood level rim of the shower it would not flood the fixtures below, it would simply go down the drain because the vents are tied into the drain. The reason the vent must be tied in 6" above the flood level rim of the fixture is because if it weren't you would never know you have a clog because the waste would drain through the vent and down the drain.

 

[Karl Knudson]

I should update this post as I have found a solution that should work well and satisfy the code requirements. I was able to get a 13 1/2' length of ABS to fit in the thick wall next to the 4" stack. That vent will tie in before it exits the roof on the second floor. The drop to the trap is about 16". Thanks for all of the help and making me think harder and look for a better solution.

 

[Jadnashua]

FWIW, you can't just cut and paste a picture to your posts, you have to use the upload function in manage attachments.

 

[Karl Knudson]

Thanks for the heads up, it should be fixed now