Please tell me if this venting setup will work correctly.

[zz_denis]

Hi, I've been a long time lurker on these forums, and finally had a question that I could not find an answer for, so I decided to register.

Im in the process of building a brand new bathroom in my house (a single story bungalow), and wanted to run this "diagram" by the plumbers on this forum. This room will be brand new (formerly part of a bedroom), so there is no existing plumbing. I took the image off the internet, and modified it to reflect my situation. The only difference is that I will have a shower stall instead of the bathtub on this picture, but that doesn't matter for the purposes of this thread.


note: the shared "wet" part of the shower vent will be 2.5", not 2" like the picture says.
The 3 drains will merge into a single 3" pipe that will run horizontally approx. 20', before dropping down into the main drain line in the basement. The pipe will run perpendicular to the wall where all the plumbing is.

My main problem is that I will not be able to run a dedicated vent for the wall-hung toilet. Will the 2 shared vents for the sink/shower be sufficient?
I would prefer to keep the diameter of these 2 vent pipes going into the attic/roof to a minimum. The wall in question is not load bearing, but it is only 2"x4" framing and it will be fully tiled, with wall hung toilet and a heavy vanity hanging on it, so I don't want to compromise it any more than I have to by cutting huge holes in it for the vents. Will 1.5" diameter for each pipe be sufficient? Can I get by with less?

Above the sink will be a recessed cabinet, and above the toilet will be the in-wall tank, so I obviously cant run a vent pipe straight up at those locations.

Any other problems you guys see with this setup? Im located in Ontario, Canada but im not too concerned with the code (the house is not getting sold or inspected any time soon. I just want it to work and drain correctly. Any help or recommendations greatly appreciated!

 

[krik]

Yes, but the sink as shown isn't vented. Run the sink trap arm horizontal direct into to the 1.5" "vent" with a santee, or drop the vent down below the recessed cabinet and then run it horizontal to end up above sink. You may have enough room between cabinet and studs to not have to cut into them. Worst case you need to run 1.5" through a single stud for either vent or drain. I would not go smaller than 1.5"

 

[Sponsor]

 

[zz_denis]

Thank you for the reply!
Wouldn't the vertical 1.5" "vent" serve as a vent for the sink? It would connect the the sink drain pipe as soon as it makes a 90 degree turn bellow the floor. The total run of the sink drain would be about 3' (2 vertically and 1 horizontal) before its connected to the "vent".

I thought about doing what you suggested, but that would mean that the section of the pipe running through the floor would be considered a "wet" vent (for the toilet) and would need to be larger in diameter (and thus a problem). The way I have it pictured, the "wet" section (bolder black in my picture) would be bellow the floor, and making it bigger would not be a problem.

 

[krik]

Thank you for the reply!
Wouldn't the vertical 1.5" "vent" serve as a vent for the sink? It would connect the the sink drain pipe as soon as it makes a 90 degree turn bellow the floor. The total run of the sink drain would be about 3' (2 vertically and 1 horizontal) before its connected to the "vent".

I thought about doing what you suggested, but that would mean that the section of the pipe running through the floor would be considered a "wet" vent (for the toilet) and would need to be larger in diameter (and thus a problem). The way I have it pictured, the "wet" section (bolder black in my picture) would be bellow the floor, and making it bigger would not be a problem.

The part above the floor is an s-trap at the moment, which means the water going down the vertical part will cause siphoning. If you can tie in the shower wet vent between the toilet and the sink drain, the the sink piece is just a drain and could be 1.5. Not sure what fitting you'd use to bring em in side-by-side anyway.

 

[zz_denis]

The part above the floor is an s-trap at the moment, which means the water going down the vertical part will cause siphoning. If you can tie in the shower wet vent between the toilet and the sink drain, the the sink piece is just a drain and could be 1.5. Not sure what fitting you'd use to bring em in side-by-side anyway.

I was under the impression that a drain could run a certain distance before it creates enough suction to siphon the water from a trap. I recall this was around 4 feet? I could be (and probably am) wrong. Either way, I could easily do either of the 2 things you suggested in the first post. Would one be preferable over the other? I could run the trap arm horizontal to the "1.5 vent" thus eliminating the need for the drain pipe bellow the sink that is currently in my picture.
If I leave both drain and the vent pipes in place (as they are currently pictured), but ran a horizontal pipe from the 1.5 vent to the drain above the sink, would this be preferable by providing an easier path for venting the toilet? (as the vent bellow this connection going down and through the floor would no longer be considered "wet")

Forgive me if I'm reading your post wrong, but are you saying that the secondary wet vent for the toilet (shared with the sink drain) is not necessary? Would the 1.5" shared shower vent provide sufficient venting for both fixtures? There will be instances when both shower and toilet are used at the same time.

 

[krik]

yes a trap arm can run a certain distance *horizontally*, but not vertically. I would go sink trap -> 90 deg horizontal -> horizontal arm -> santee into the 1.5" "vent" to keep it easy. Leave everything else as is - trying to further combine will run into problems with respect to wet vent sizing and the order in which fixtures get added.

 

[hj]

DO NOT try to "rationalize" it. The sink drain as shown is ILLEGAL under EVERY code. Also, where are you going to get the 2.5" stuff for the "common wet vent" portion? Most codes would require one of the vents to be 2" for the toilet.

 

[zz_denis]

yes a trap arm can run a certain distance *horizontally*, but not vertically. I would go sink trap -> 90 deg horizontal -> horizontal arm -> santee into the 1.5" "vent" to keep it easy. Leave everything else as is - trying to further combine will run into problems with respect to wet vent sizing and the order in which fixtures get added.

Understood regarding the vertical drop. If I do as you suggest, should I remove the current sink drain as per my original picture all together and end up with this:



Will the dual 1.5" wet vents provide sufficient venting for the toilet?


Another question - the drain from the toilet goes straight down through the floor and then makes a 90 degree turn to run parallel to the floor. Only after this 90deg turn will the 2 "vents" connect to this drain. Wouldn't this create the same problem (siphoning the water from the toilet trap) as my original sink venting setup?

DO NOT try to "rationalize" it. The sink drain as shown is ILLEGAL under EVERY code. Also, where are you going to get the 2.5" stuff for the "common wet vent" portion? Most codes would require one of the vents to be 2" for the toilet.

I'm not trying to rationalize it. I have no problem doing it like krik suggested. It will actually work better for me as it will eliminate one pipe going through the floor. I simply wanted to understand why, and I did.
Whats the problem with getting a 2.5 pipe for the common section of the shower vent? Is this size not available?
Please forgive me if my questions look silly. I am relatively new to plumbing and still learning.

 

[Terry]

There are no 2.5" pipe and fittings.

You need to run 2" as a vent for the toilet. That can be done on the lav side or the shower side.

 

[zz_denis]

There are no 2.5" pipe and fittings.

You need to run 2" as a vent for the toilet. That can be done on the lav side or the shower side.

Thanks for clearing that up!

If 2.5" is not available, I could use 3" for that part (if needed).

Do I REALLY need a 2" vent for the toilet? Wouldn't TWO 1.5" shared vents actually allow more air than a single 2" vent would? All 3 fixtures will never be used all at the same time. I really don't want to cut a 2" hole through the framing of this wall unless I absolutely must...
Again, I am not too concerned with the code as long as the system works properly.

 

[MKS]

Terry and HJ, I believe 80 plus years of plumbing education and experience, give advice to us diyers that WILL pass code and careful inspection. No disrespect krik.
Thanks for this site.

 

[Reach4]

Wouldn't TWO 1.5" shared vents actually allow more air than a single 2" vent would? All 3 fixtures

Two 1.5 pipes have a little more area than a single 2 inch pipe. For a 1.5 inch pipe, you would need at a 2 inch hole if you can insert it straight.
http://www.engineeringtoolbox.com/pvc-cpvc-pipes-dimensions-d_795.html

The code rules require things that may not seem logical.

 

[krik]

No disrespect krik.
Thanks for this site.

??? don't believe I gave any advice that wouldn't pass code. I know my limits - mostly.

 

[MKS]

??? don't believe I gave any advice that wouldn't pass code. I know my limits - mostly.

I am not questioning your advice, knowledge or experience.
Just acknowledged you but it did not come across correctly.

 

[krik]

Just acknowledged you but it did not come across correctly.

I blame the internet haha. Was just wondering if I had said something incorrect, which I am always on the lookout for ... it's how you learn, right?

 

[MKS]

I blame the internet haha. Was just wondering if I had said something incorrect, which I am always on the lookout for ... it's how you learn, right?

Yes I have.