Trying to plumb my way out of a money pit.

[riddick021]

I have a pretty good feeling I'm going to get a few "your better off hiring a qualified plumber" comments. To that I have to say... your absolutely right and I wish we had. However, things didn't work out that way and after all the money that has been wasted on the low bid contractors my parents hired I'm afraid the only option we have now is for me and my dad to do the work ourselves. I'm not going to go into the details of our money pit but things are getting pretty bad.

That being said,

I think I have gained a pretty good grasp on BASIC plumbing design and wouldn't have too much trouble if this were new construction where I could do what ever I want with the framing. But this is a gut job and the existing framing has brought up some issues I need clarifications on (I live in Westchester County, NY so IPC applies I believe).

1. Can a soil stack be offset by 45 degrees? All the stacks I have run through walls that don't line up with the walls above. They are not off by too much and I can keep everything relatively concealed with two 1/8 bends but these will need to be on the soil portion not the vent.

2. Does a soil stack have to have a stack vent? We moved the powder room and there was no way to run the water closet arm to an existing stack without drilling through a beam or dropping the ceiling in an already low ceiling basement. I had access to the building drain because we just changed out the rotted old one so I put in a wye and plan to connect the powder room to it. Do I need to extend the 4" vertical stack to the attic with a ty or can I use a sweep and and just make a branch vent from the powder room sink to one of the other stacks? Here's a diagram (elevation view):

Vent Leader
|
| (2")
|
Lav/WC----90
|
| (4")
|
------Building Drain-------

or
VTR
|
-----------|
| |
(2") | | (2")
| |
Lav/WC-----ty
|
| (4")
|
------Building Drain-------

If I do need a stack vent can I tie it into another stack vent or does it need a separate roof penetration. I know you can combine vent stacks but I'm not sure about multiple stack vents. And finally, can I reduce from 4" to 2" since there will be no toilets on this line after the powder room.

3. I'm using no hub cast iron in the public areas. Can I tie a pvc street elbows to no hub cast iron in lieu of a closet bend?

4. Can a shower wet vent be horizontal? the lav, shower, and WC are in three separate bays with the WC in the middle so I will need to go horizontal with the shower wet vent before going vertical. This is how it looks from the top (plan view)
Lav
|
|
--------- -----------WC----Stack
|
|
Shower----------

5. How many joist can I drill through? I'm trying not to drill through any but it looks like I will have to make a few 2" holes.

[Wally Hays]

Do you know what a stack vent is? or the difference between a stack vent and a vent stack? too many vague questions there and without actually seeing what you are talking about a definitive answer is not possible. You can only drill through the middle 1/3 of a floor joist.

[riddick021]

Yes a stack vent is the soil/waste stack above the point where the highest fixture connects. A vent stack is dedicated stack for venting purposes. I've seen several diagrams where a vent stack will connect to the stack vent before it penetrates the roof but never the other way around. I'm sorry if I was vague. Basically I need to know if I have three stack vents can I combine them all to one pipe that penetrates the roof given I have room in my attic to do so. I know that about the middle 1/3 but the suedo plumber my parents hired said something about not being able to drill through two consecutive joists and so he made soffits everywhere.

[jimbo]

Yes, waste stacks and vents can have 45º offsets. You can combine vents in the attic. You have to observe code for total vent size required. For example, you can't put three 2" vents together and penetrate the roof with a 2" pipe. Broadly speaking, the total vent size needs to equal the size of the house main drain...3" or 4" usually. Certain areas ( think snow) require all vent pipes to be minimum 3" for example.

Can't really get your diagrams. But a wet vent almost by definition will be horizontal. The ONLY reason a vent can ever be horizontal below flood rim is BECAUSE it is wet, meaning it will always be kept clean by repeated waste flows. A dry horizontal vent will tend to clog with waste.