Best way to offsett DWV

[Cobalt]

Hi,

First time posting.

I am renovating an older building and want to correct some plumbing in the process.

1. The 3" stack vent was reduced to 2" above the last fixture at "B" then upsized back to 3" at "C" before it exits the roof. I assume I need to replace that section of 2" with 3" to make it 3" continuous. (The building drain is 4". There is another separate 2" waste stack and a 3" roof drain. Or is this sufficient venting?)
see Diagram D



2. I need to offset the main stack from A to B as I can't go straight up vertically because of door. Which of 3 offset methods is the best. (see diagrams)

2 x 45° offset - Diagram A
Wye - Diagram B
Tee - Diagram C

Thanks for your comments.

 

[Reach4]

I assume I need to replace that section of 2" with 3" to make it 3" continuous.

I don't think so.

I think A or B is better for inspections, because your dry vent does not go horizontal.

 

[Sponsor]

 

[Terry]

2" will vent up to three bathrooms assuming you have enough venting for the entire home other places.
Each fixture needs venting before it enters the waste stack.
A or B works for the toilet in your pictures.

 

[wwhitney]

Doesn't the vent take off for the toilet have to occur before (via a wye rolled up at least 45 degrees) or when (via a san-tee) the horizontal toilet drain turns vertical?

Cheers, Wayne

 

[Terry]

The toilet can be vented many ways. The bowl siphons, and then gets refilled by water in the tank.
All of the other fixtures are plumbed so that they don't siphon.

 

[wwhitney]

So it's OK for the sequence to be

closet flange -> closet bend -> 54" horizontal run -> quarter bend -> upright wye with side branch for vent takeoff?

Because that's what diagram B shows.

Cheers, Wayne

 

[Terry]

Yes, only for toilets though.

 

[hj]

And only if you have an intelligent inspector who knows how toilets work, which is not always the case.

 

[wwhitney]

Thanks, I get it now, toilets have different rules for the trap arm because the actual trap is internal to the toilet.

I see that UPC Table 1002.2 Note 2 just says that the developed length from closet flange to the vent shall not exceed 6 feet. And UPC 1002.4, which requires the vent takeoff not to be below the weir of the trap, excludes toilets.

Cheers, Wayne

 

[Cobalt]

Thanks to Terry and everyone else for your input.