Hi All -

I've seen similar questions asked and answered but want to ask specific to my project.

There are 4 bathrooms currently in the house (it is a converted single family to 4 unit multi-family; this multi-family conversion likely took place in the 1930s, the house was originally built in 1875.

I have a single 4inch cast iron soil stack that runs from the basement to the attic. The 2nd floor bathrooms T- off the soil stack and have a separate dry vent which runs up through roof. My guess is the current 4 bathroom venting config dates back to the time of conversion - except for the second floor vent which is PVC - I'm guessing this was added in the 1980s by previous owner.

My goal is to install a third floor/attic bathroom situated directly next to the current dry vent main cast iron soil stack and convert the dry vent to a wet vent. In addition, to support the third floor plumbing, a new 4inch vent will be cut into roof. The third floor bath is intended to have a toilet, lav sink, shower stall, and claw foot tub.

My question - will this setup pass the mustard? I am located in Rochester, NY.

Thanks!
Dan

Welcome to The Plumbing Page,

Quote:

---

My question - will this setup pass the mustard?

---

It will not only fail to pass mustard it won't even cut it.
1. The third floor vent's unnecessary
2. You are discharging a vented WC#3 past a unvented WC#4
3.The first floor toilets are unvented and you're discharging three bathroom groups past them
Back to the drawing board! Good luck, Tom

Thanks Tom.

With respect to the 1st floor bathroom venting, If I installed a 3-inch PVC dry vent that ran parallel to the stack and tee-d in right above the 1st floor sewage lines - would this solve the 1st floor problem?

With respect to the 2nd floor bathrooms - I do not believe the 2nd floor flow bathrooms flow past each other. I just drew it that way.

How do high-rise apartment buildings work? I cannot believe they have separate venting for each floor.

I have read some things where the fact that it's a vertical stack and 4-inches makes a difference, but I admit I have not been able to find (or understand) the code the makes this legal.

Thanks for your help.

Quote:

---

If I installed a 3-inch PVC dry vent that ran parallel to the stack and tee-d in right above the 1st floor sewage lines - would this solve the 1st floor problem?

---

Sorry but no! I'm looking at two bathroom groups on the first floor, Your way would still have the two upper floors discharging into the first floor vent.
What you could do id combine the two first floor vents and revent back into the second floor dry vent at least 6" over the top of the highest flood rim.

Quote:

---

With respect to the 2nd floor bathrooms - I do not believe the 2nd floor flow bathrooms flow past each other. I just drew it that way.

---

If you didn't want me to read it that way you shouldn't have drawn it that way. But it makes no difference because the first floor's still unvented.

Quote:

---

How do high-rise apartment buildings work? I cannot believe they have separate venting for each floor.

---

Code says that every fixture that has a trap MUST be vented. However, If you connect a 2" dry vent in the main an d run it to the roof you mat revent all your fixtures back to that vent PROVIDING you keep it dry all the way to the roof. That way way you would have only one vent exiting the roof.

Quote:

---

I have read some things where the fact that it's a vertical stack and 4-inches makes a difference, but I admit I have not been able to find (or understand) the code the makes this legal.

---

When you find it please pass it along to me. Good luck, Tom

Thanks again Tom...

I figure it might be easier to diagram it how it should probably be done and see if this passes the mustard...

The blue lines are dry vents, the violet lines are wet vents. Red lines are soil lines that are proposed. Most of the blue lines are new work. And depending on how these lines are run, the two dry vents from the first floor up may be combined into a single dry vent. The interior walls which these would run through are eight feet apart. (this will be a lot of work... ugh!)

Alternatively, Is it acceptable to run a dry vent along the outside of the house??