I am finishing our master bath in our 3 year old house. I have the layout finalized and need some additional info on venting. I have done a lot of research on this and other forums, bought the Code Check and Black and Decker plumbing books. It seems the more research I do, the more confused I get. I understand most of what is going on, but want to make sure it is done properly. I have met with the Code Enforcement Officer from my town and plan on having him inspect the final job. I am bound by the UPC code and found some errors that he passed on the original inspection of the plumbing a licensed plumber did. He allowed a 3" vent horizontally to vent the shower/tub and toilet in the basement which I thought was a no-no. I just want to make sure I do this properly.

OK so here is a picture of my layout:

I am planning on using a double fixture fitting for the sinks and adding a 2" vent to the attic. In the pic you can see a 2" future vent they left me which stubs from the basement to the attic vertically @ 10' and then horizontally roughly 9" then stubs up to a 3" through the roof. The tub can either drain left or right, the shower drain is fixed as drawn. The toilet can be either on the MB wall or the bedroom2 wall. We would prefer the Bedroom2 wall.

My questions are do I need a separate vent to the tub? If I right drain the tub I can tie into the drain from the vanities right? Can the vent from the vanities handle the tub or would I add a new vent and tie into the vent from the vanities above the 6" flood line?

For the shower, should I put a new vent in the shower wall that would serve the Shower an Toilet? Also when my vents meet in the attic, do I need to up-size the pipes? Can any portions of the tub or shower act as wet vents to limit the amount of venting?

I would like to keep my main drain in the center of the basement if possible so I can limit bends and build a soffit around them.

Any help would be greatly appreciated.

Thanks, Steve

Does this work? Can the toilet drain turn in drain to the front or does the drain have to turn and go behind the tank? I can not get a vent into the left wall by the shower from underneath due to a floor joist being directly under the wall cavity. I was planning on going into the the shower wall, which does not go to the ceiling, turning horizontal to vertical then proceed up to the attic through the wall between bedroom2 and shower. I will then abandon the future vent in the first drawing. I would like the drains for the WC & Shower to be in the same floor joist cavity to eliminate drilling floor joists.

I believe I have a total of 9 DFU's for the bathroom group. Can I use a 1 1/2 vent for the tub/vanity and then tie to the 2" from the shower/WC? I can't find a lot of info on critical distances for the drains to the vents.

Any info will be greatly appreciated. I am completely behind the 8ball on this job as I told my wife she would be able to take a bath in her new tub by the time she Graduates from college. Which is in a month. Yikes!

Thanks, Steve

Anyone?

I can see a number of small problems on your proposed layout.

1. On the branch drain which is serving the W.C. & shower you show a cleanout on the end of the line with a wye & 1/8bend and a fixture arm to the shower, then another wye & 1/8 bend with a short horizontal offset to the vent riser. In that configuration you have a horizontal offset on the vent below the floor, but code prohibits any horizontal offsets on a vent until the vent reaches an elevation at least 6" higher than the flood level rim of the highest fixture served by that vent, which in this case you be 6" higher than the W.C. bowl rim.

You could place the shower arm wye between your proposed location for the cleanout and the vent. In this manner the vent would be on the downstream side of the shower arm and assuming the vent rises vertically you would be ok.

For the branch serving the W.C. and the shower the combined fixture load is 4dfu's and an 1-1/2" vent is rated for up to 8dfu's, but note the subscript 2 beside the dfu number. If you look at the second exception on the chart it says NO W.C. A wc requires a 2" vent.

On that branch you only need a 3" drain until you reach the wye at the WC. From the WC wye to the shower and vent it can be 2" but be careful here as well. On the top of the drawing it shows the 2" vent has a horizontal offset to the vent through the roof. If any horizontal offset on a vent line exceeds 3' the entire vent line must be increased one nominal trade size. That means the entire vent would then be 3" and the drain line downstream from that vent opening would also need to be 3".

If you have enough vertical clearance in the attic space you could make that offset rise at a 45degree angle because in plumbing any line that rises at an angle of 45degree or greater is said to be a vertical line.

The lavatories are rated at 1dfu which would be an 1-1/2" drain line, but code will allow us to increase the drain line by one nominal trade size, which would then be 2".

A 2" fixture arm is allowed to go 5' from trap weir to vent opening. I roughly scaled your drawing and you should be able to run a 2" line from the tub and tie the vent in at 5'. The vent should then rise between the two lavatories very close to the left hand lav as facing the lavs from the front. You could then run a 2" over to the other lav and still be under the 5' maximum, thus you would not need two vent risers on this wall.

The total dfu load for the tub and two lavs is 4dfu's which could be vented with an 1-1/2" line, but since you have a horizontal offest greater than 3' the vent must be increase one nominal trade size, which would be 2" which you have already specified.

One question on the vents running horizontally in the attic. These runs are both longer than 3'. If I run the vent straight up through the roof on the shower/WC vent and serve that with a 2" I can then tie the vanity/tub vent into that. I do not have enough clearance to go @ 45 degrees in the attic with that vent so this will have to be horizontal( pitched of course). If I sized the vent for the Tub/Vanity to 2" to accommodate a trap arm distance of 5', would the entire vent need to be up-sized to 3" both horizontal and vertical, or only the section in the attic which goes horizontal? If I do then I think I could run 1 1/2" vents from the tub, into the vanity (as shown in drawing) and then only have to up size to 2" due to the horizontal length and do away with wet venting. Does this make sense?

I am going to adjust my drawing and re-post. Would it be OK to email you my updated drawing for further critiquing from you. I am hoping on doing this job this weekend.

Thank you very much again,

Steve

Thanks again for all your help. I really appreciate it.

So I have done all my critical measuring in my bathroom. I think I have a firm grip now on the codes and how to meet them with your suggestions.Her is my updated drawing:

Lets start with the Vanity/Tub:
1. You stated, “If any horizontal offset on a vent line exceeds 3' the entire vent line must be increased one nominal trade size”. In my new drawing I plan on taking your advice and running the 2” drain from the tub to the vent riser. I can meet the <5’ rule for the trap arm on this. I assume this rule applies to all horizontal piping after the trap weir on this arm to the vent riser?
2. On the right Lav (facing the Lav), you had mentioned to size that drain to 2” to meet the 5’ rule. This measurement actually comes in just under 3’6”. If I position the vent riser in this manner I can meet both critical distances from the tub and Lav. I think I read in my code book that a 1 ½” trap arm can extend a max of 3’6” from the trap weir. Will this work to tie into the fixture fitting and the 2” drain/vent riser or does it have to be up-sized to 2”?
3. Now with the Lav/Bathtub only being 4DFU’s and only requiring a 1 ½” vent, I can up-size this vent to 2” and now run horizontal on this section in the attic? It will roughly run 10’. If this all works this should take care of this side of the Bathroom.

Now for the WC/Shower side: This gets a little tricky. I found that I have some blocking interfering in the wall cavity, which I was going to run my vent to the attic in. Her is what I came up with if it will work.
1. In the drawing I show the vent pipe coming straight up, or maybe at a short 45° and then up in the new shower wall cavity. Then I planned on going 90° to a horizontal line for about 18” and then 90° back through a different empty wall cavity about 14” total length, then to a 90° vertical to the attic. Once I hit the attic I plan on running 45° vertical to a new stub through the roof. The entire horizontal will be more that 6” above the toilet rim.
2. Now, the code states I have to have a 2” for the WC, and I can’t go more than 3’ horizontal without up-sizing to 3”. I want to try to keep the pipe at 2”, so by limiting the horizontal to less than 3’, and 45° in the attic will this work for that group?

If this all works can the two 2” pipes be connected in the attic and stubbed up through, or does my stub through he roof have to be 3”? I thought I read somewhere the roof stub had to be 3”.

Also what can I use to tie the toilet and shower together? These both fall in the same floor joist cavity, so I use a Wye, or could I use 3” combo with a 2” reducer and come straight into the back? I also plan on putting a clean-out on the end of the shower drain.

Sorry for the long post, I hope I made a clear view and used your advise properly. I greatly appreciate you help.

Thanks so much,

Steve

Thanks again for all your help. I really appreciate it.

Sorry I don't know why the first post came through all mixed up....

I have done all my critical measuring in my bathroom. I think I have a firm grip now on the codes and how to meet them with your suggestions. Here is a new drawing:

Lets start with the Vanity/Tub:
1. You stated, "If any horizontal offset on a vent line exceeds 3' the entire vent line must be increased one nominal trade size". In my new drawing I plan on taking your advice and running the 2" drain from the tub to the vent riser. I can meet the <5' rule for the trap arm on this. I assume this rule applies to all horizontal piping after the trap weir on this arm to the vent riser?
2. On the right Lav (facing the Lav), you had mentioned to size that drain to 2" to meet the 5' rule. This measurement actually comes in just under 3'6". If I position the vent riser in this manner I can meet both critical distances from the tub and Lav. I think I read in my code book that a 1 1/2" trap arm can extend a max of 3'6" from the trap weir. Will this work to tie into the fixture fitting and the 2" drain/vent riser or does it have to be up-sized to 2"?
3. Now with the Lav/Bathtub only being 4DFU's and only requiring a 1 1/2" vent, I can up-size this vent to 2" and now run horizontal on this section in the attic? It will roughly run 10'. If this all works this should take care of this side of the Bathroom.

Now for the WC/Shower side: This gets a little tricky. I found that I have some blocking interfering in the wall cavity, which I was going to run my vent to the attic in. Her is what I came up with if it will work.
1. In the drawing I show the vent pipe coming straight up, or maybe at a short 45* and then up in the new shower wall cavity. Then I planned on going 90* to a horizontal line for about 18" and then 90* back through a different empty wall cavity about 14" total length, then to a 90* vertical to the attic. Once I hit the attic I plan on running 45* vertical to a new stub through the roof. The entire horizontal will be more that 6" above the toilet rim.
2. Now, the code states I have to have a 2" for the WC, and I can't go more than 3' horizontal without up-sizing to 3". I want to try to keep the pipe at 2", so by limiting the horizontal to less than 3', and 45* in the attic will this work for that group?

If this all works can the two 2" pipes be connected in the attic and stubbed up through, or does my stub through he roof have to be 3"? I thought I read somewhere the roof stub had to be 3".

Also what can I use to tie the toilet and shower together? These both fall in the same floor joist cavity, so I use a Wye, or could I use 3" combo with a 2" reducer and come straight into the back? I also plan on putting a clean-out on the end of the shower drain.

Sorry for the long post, I hope I made a clear view and used your advise properly. I greatly appreciate you help.

Thanks so much,

Steve

So I started digging into my walls today. I have some restrictions/limitations in the shower walls where I proposed my vent for the WC/Shower. I am now going to turn the toilet so the back faces the Bedroom2 as in drawing #1. The Master Bedroom mate wall houses a pocket door so I am building a false wall in front of it. I plan to run the vent up this wall into the attic. I believe this will make things a lot easier. I will also be putting some shelving for the toilet in this wall.

So my question is this, can I extend the 3" past the WC and stub my 2" trap for the shower into it with a 3"x3"x2" Wye with a clean-out on the end, or do I reduce it to a 2" drain past the WC to the shower? I read a 2" horizontal wet vent can handle 4 DFU's and a 3" 8 DFU's. Would this be considered wet venting, or is it just a trap arm length critical distance? The new 2" vent location would end up 56" downstream from the trap weir of the shower, and 20" downstream of the WC. If I am correct, the toilet needs to be within 6' of the vent and the 2" Shower drain within 5'. I will then proceed vertical to the attic and 45* to a point where I can stub through the roof.

I think this will work right?

Thanks, Steve