[Creative55]

Hello,
I would like to install a bathroom and would like to know if my proposed plumbing diagram venting will work? The original plumber who scoped it out said I should run a 3" drain but I hear a 4" (as marked in the drawings) is what is normally used. The slope will be a 1/4 drop for every foot.

Thank you.

[Mike45plus]

Creative,
Yes, it will work however, a 3" drain would be just fine and code compliant. The IRC and IPC do not require an individual vent for the toilet as long as there is a 3" vent stack or stack vent connected to the dwv system...

[ma0641]

If your local code allows, use an AAV under the sink. Saves running pipe.

[Milo Dolezal]

Nice drawings !

3" drain is perfectly OK... You can combine all vents into one, 2" vent, about 48" above the floor, and continue with 2" vent above roof line

We don't use 1 1/4" vents, but 1 1/2"

Hope that helps

Milo

[Creative55]

Creative,
Yes, it will work however, a 3" drain would be just fine and code compliant. The IRC and IPC do not require an individual vent for the toilet as long as there is a 3" vent stack or stack vent connected to the dwv system...

Thank you Mike45plus,
Is there any advantage to running a 3 over 4 inch drain?

Nice drawings !

3" drain is perfectly OK... You can combine all vents into one, 2" vent, about 48" above the floor, and continue with 2" vent above roof line

We don't use 1 1/4" vents, but 1 1/2"

Hope that helps

Milo

Thank you Milo, would it make things flow smoother if I used a 4 inch drain?

If your local code allows, use an AAV under the sink. Saves running pipe.

Thank you, what is a AAV?

[ma0641]

"Thank you, what is a AAV?"

Air Admittance Valve also called a Studor. In some cases it replaces a roof vent and is very useful in retro fitting and with kitchen islands. Our peninsula sink and basement bath vanity use them. They are not accepted at all locations so check with your plumbing codes.

[Milo Dolezal]

Creative55:

We size pipes according to number and type of plumbing fixtures. Each plumbing fixture has assigned number of "plumbing units." In your case, you are adding toilet (3 units), sink (1 unit ), and shower (2 units ) which amounts to 6 plumbing units. So theoretically speaking, you could triple the load to max the pipe out as horizontal load for 3" pipe is 20 units / 2 toilets maximum. Moreover, 3" pipe is easier to install, fits better in tight spaces and fittings are lot cheaper than in 4" size ... However, if you do it in 4" pipe, it will be perfectly OK to do.

Hope that explains

Milo

[Creative55]

"Thank you, what is a AAV?"

Air Admittance Valve also called a Studor. In some cases it replaces a roof vent and is very useful in retro fitting and with kitchen islands. Our peninsula sink and basement bath vanity use them. They are not accepted at all locations so check with your plumbing codes.

OH... got it, thank you very much for you help.

Creative55:

We size pipes according to number and type of plumbing fixtures. Each plumbing fixture has assigned number of "plumbing units." In your case, you are adding toilet (3 units), sink (1 unit ), and shower (2 units ) which amounts to 6 plumbing units. So theoretically speaking, you could triple the load to max the pipe out as horizontal load for 3" pipe is 20 units / 2 toilets maximum. Moreover, 3" pipe is easier to install, fits better in tight spaces and fittings are lot cheaper than in 4" size ... However, if you do it in 4" pipe, it will be perfectly OK to do.

Hope that explains

Milo

Thank Milo, I wasn't aware of the assigned numbers "plumbing units" I appreciate your detailed explanation!