Basement ceiling -main drain connection

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Daniel7

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Hello everyone. Could anyone help with a question about DWV best practice? I'm installing 3' and 2" waste lines from upper level to connect to the main 4" house waste line along the ceiling of the Basement. This question is so much about what is allowed by plumbing code - but what is best practice for best quality flow.

Question:
1.
Which option does everyone recommend? See attached drawing that I drew up. I'm leaning towards OPTION A where I can as the best approach. And using OPTION C as second best option where OPTION A is not possible. Is this correct? Or is something different even better?
OPTION A - Connect at a 45 degree both in plan & elevation to the main 4"
OPTION B - Connect at a 45 degree laterally to the main 4"
OPTION C - Connect at a 45 degree vertically from above to the main 4"

2. Also - is there a benefit to sloping the main 4" line more than 1/4:12? Or should I just stick with 1/4:12?

Project Information:
This is for a residential project, ~2,500 SF house major renovation in Portland, Oregon. Using ABS DWV piping. Using the current International Residential code.

Thank you everyone! I very much appreciate and respect your insidghts,
Daniel
 

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Aaroninnh

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Im having a hard time following your drawing. Is the bottom part upside down?

I'd suggest any time you have a major change in direction to try to have a cleanout, so use a tee wye and put a cleanout plug in it. Also, as to slope, 4" pipe can be as little as 1/8". I wouldn't use more than 1/4" as it can also cause clogs as it can make the water speed past the solids the water is carrying, leaving them behind.
 

Daniel7

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The 6 options are confusing Id go top left and bottom left
Sorry about the confusion everyone. The drawings show only three options - from left to right. The drawing at the top shows a floor plan view, the bottom shows an elevation of the same option. I'm an architect - so this is the standard way I draw to understand something - drawing the same thing in both floor plan view and in elevation view :)

I'll draw up and post another diagram for better clarity.
 

wwhitney

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They all will work. Is space taken up in the basement not a concern? If it is, then Option C, with the horizontal portion of the 2" drain in the floor framing (and so likely not run at a 45 as you have it) is a good choice.

Otherwise, Option A uses the least degrees of turn on the 2" drain, so that's nice.

Note that Options A and C, as drawn, both require a 60 degree bend. Which is fine, I just have never understood why they are made with the radius of a quarter bend instead of the radius of a 45 or LT90.

Cheers, Wayne
 

Daniel7

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Thank you everyone for the feedback! Some notes:

1. I prepared an updated drawing showing the three options - see attached drawing. This is an elevation view only for clarity. And I've labelled the fittings.

2. There is no concern about maximizing headroom clearance, etc. The only goal is using the installation that is most efficient and has the most efficient flow.

It sounds like everyone is in agreement that option A is the best! As I was preparing the drawings it seems very obvious now that option A is most efficient because it has least abrupt change in direction.

Best,
Daniel
 

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Daniel7

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Quick follow up for curiosity sake. I asked my question to Chat GPT - Open AI's artificial intelligence engine. Here is the AI's response:


My question:
I'm installing DWV rough-in for a 2,500 SF house in Portland, Oregon in the US. I'm using ABS piping. Which will allow for better flow: option 1 - connect waste lines laterally to the main sewer line or 2 - connect waste lines to the top of the main sewer line? Both options would use a wye fitting

Chat GPT AI's response:
Both options will have similar flow performance, as long as the pipe sizes and fittings are correctly sized to handle the volume of waste water. The main factor in determining which option is better is the layout of the plumbing system, as well as local building codes. Option 1 (lateral connection) may be preferable in situations where the main sewer line is located at a higher elevation, while option 2 (top connection) may be preferred in situations where the main sewer line is located at a lower elevation. It's important to consult local building codes and consult with a licensed plumber to determine the best option for your specific installation.
 

Tuttles Revenge

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Up until a few months ago I would have said a wye entering from the top would be the best. But after using a camera down a drain to track down a belly in a house and watching toilets flush into the main drain from both the top and from the side connected with wyes.. they all cause waste water to flow both down and upstream.. significantly. I didn't have time to determine which was worse, but I suspect it was the wye / combo entering from the top that was the worst.
 
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