Bath Addition Question

[User101]

Hi everyone,

This is my first post here and I hope I can get an answer to my project question. I need to install a bathroom addition to an existing room in the home and when I'm going to run the sewer line it will enter the bath addition almost in the corner of the room. I'm not a plumber but I drew a diagram to show you my project and see if my plumbing setup is correct or wrong. If the plumbing setup is wrong and will cause problems please let me know how can I put the setup better. Thanks

 

[MicEd69]

We need pipe sizes, some dimensions and proposed fittings. Also, we need to know what is downstream from the tie-in to the main, where the main stack is located, and possibly the layout of the existing bathroom.

 

[User101]

Hi MicEd69,

Thanks for trying to answer my question. I edited the drawing with pipe sizes and uploaded one more drawing for the info you requested. Hope now is much clearer.

 

[Twowaxhack]

Use 4” for the sewer. Install plenty of cleanouts.

 

[User101]

Hi Twowaxhack, thank you for the suggestion. Yes that would be necessary.
Beside cleanouts, is there a problem when the new 3" or 4" sewer pipe enter the bathroom at the corner of the room? and what about the setup of plumbing? is the venting location correct?

 

[MicEd69]

Something like this would be good.



The toilet and shower are wet vented through the sink drain and vent. The vertical line should be 2" and continuous through the roof. The horizontal drain line from sink can be 1 1/2" to the 2" vent/drain line. The shower and the drain from the sink should be 2" until they meet the line where the toilet is located. The line from the toilet to the main can be 3".

Is your house on a slab? The only issue you may have with the sewer going under the corner of the existing building is with possible foundation interference whether you are on a slab, crawl space, or basement. But there would not be any problem exiting straight to the street and then 45 over to the main.

Note the cleanout as Twowaxhack mentioned. And depending on the fittings required to get to the main, more may be recommended.

 

[MicEd69]

Use 4” for the sewer. Install plenty of cleanouts.

Why would you want to use a 4" sewer line for 6 DFUs, when a 3" line will handle 20 DFUs? Wouldn't you want the higher velocity afforded by the 3" which is only handling a single toilet?

 

[Twowaxhack]

Why would you want to use a 4" sewer line for 6 DFUs, when a 3" line will handle 20 DFUs? Wouldn't you want the higher velocity afforded by the 3" which is only handling a single toilet?

Most codes require 4” sewers. Once it hits 3’ outside the foundation it becomes a sewer. Inside the foundation it’s the building drain.

 

[User101]

Thank you so much MicEd69 for the picture and the detailed information you provided. Now it looks much clearer for me on how to setup the pipes. I just drew one more picture to show you if I understood it correctly.



thank you

 

[MicEd69]

Yes, you are getting closer. The horizontal connections to the downstream lines need to be at a 45-degree angle; that is the shower to the 2" and that 2" to the 3". And as Twowaxhack mentioned, the line 3" outside the building may need to be 4" after it passes 3' from the building. I would check with your local authority and see if that line has to be 4" to the main.

The sink connection to the vertical drain/vent should be a 2x2x1 1/2 reducing sanitee. The distance from the shower to the wye cannot be more than 8'. And the distance from the 2" riser drain/vent for the sink to the wye cannot be more than 8'. And all lines need to slope 1/4" per foot. I think your layout can handle those dimensions without an issue.

You might be able to get by with a 2" cleanout in the vent riser, and one outside the building.

 

[Twowaxhack]

If it’s legal to run 3” then that’s fine. It’ll work wetter they say it’s legal or not but I’d hate for you to get busted on a technical foul.

 

[User101]

Thank you so much MicEd69, I edited my drawing, Please let me know if now looks correct. Yes I will put 2 cleanouts one inside and one after the pipe leave the building.

Also, Thank you Twowaxhack for your suggestion to use 4" for outside sewer line as well to meet the code.

 

[MicEd69]

You are welcome. And remember the 2" from the shower to the 2" from the sink is also a 45 connection.

 

[User101]

You are welcome. And remember the 2" from the shower to the 2" from the sink is also a 45 connection.

Yes, I will pay attention to that. Thank you again for all the details and information you provided. I think that will also help people in the future as well with same situation I have.