I am looking to add a 3rd floor bath(toilet+sink) to EXISTING 2nd floor bath plumbing, but I want to know if my planned piping and venting will work.
See attchd file
Existing 2nd floor bath layout is in BLACK lines
New Plumbing for 3rd floor is RED lines
I will put in a 3"WYE at the 2nd toilet flange junction so I can continue 3" horizontal pipe an additional 5' where it will turn 90deg. Up into wall to go to 3rd floor, other end of this WYE will reconnect to existing toilet flange.

Any info is much appreciated

Has a permit been pulled and will this job be inspected? Because if it will be you're in for a very interesting chat with the inspector. I can see three code violations on the second floor and a couple more up on the third. You say the second floor's already in? Was it inspected and passed? Where do you live and what Plumbing Code do you fall under?
I'll wait for other experts opinions before I comment farther. Regards, Tom

I'm not an expert in plumbing so I'll leave the code violations to speedball.

If it is at all possible to take out the 90 degree in your waste drainage you should.

Have you considered the drop into your floor over the 5 foot horizontal. I do industrial pipefitting and the drop there is an inch each foot as a minimum and that's not poop. A lot of places require 12 degree drop in the pipe.

Remember sh*t flows down hill.

Your plumbing is set up for some serious backup problems, assuming the plumbing was done with correct drop your toilet drains by your sink, and your vent should not be the last thing on the line before your four " I hope you have check valves on every thing.

Since I work under UPC - you don't want me to comment. My Code violations count could beat Tom's.

Hi all:

Like Tom and Milo said... no matter what code you're under none of this will pass code requirements and you can expect all kinds of different issues.

I can draw up the correct way to pipe all this, but need to know what code you fall under (call local plumbing inspector or your local library) as Tom has asked about and if the piping is exactly as you drew it or did you make any mistakes... 'cause something's off...

As Tom asked... was this inspected on 2nd floor? Is there a bathroom directly below this bathroom on 1st floor?

Let us know all you can and I'll pop back in and draw up it all up... ;)

MARK

Thanks all for your comments.Since I have not had any issues over the years with the existing bathroom/laundry, I decided to investigate.My diagram was from one drawn up years earlier prior to my living here. I opened some observation holes in the ceiling and wall for the 2nd floor bath and found some interesting things, see my new, more accurate drawing. Also note, the stack from the cellar is 5" cast iron.
From what I can see, the vent for the existing bath(2nd floor) SINK extends from the junction of the 1 1/2" sink drain and the extension leading to the p trap. It goes up the wall, over the ceiling and up through the roof. I cannot see if the 2" laundry connects to the vent. Regarding pitch, this is a colonial building in MA and the floor joists are true 2"x10", so pitching the drains 1/4-1/2 inch per foot is not a problem.
I would like to know if it is feasible to add the 3rd floor bath, if so how would I vent?
Again, thanks for taking the time to comment.

Which codes are we talking about in particular, as I said residential plumbing isn't my strong point since my craft is industrial (steam/WOG) application. I assume the venting is a violation because its location could just as easily make it a siphon, and I'm sure the lack of drop is probably a code violation... what did I miss? I'm curious

It can certainly be done...

Just need to make a few changes.

SOUNDS like the toilet and tub are wet vented by the lavatory vent on the 2nd floor, but it's not what you have drawn? You show the laundry... vent must connect back to the 2" vent. There is a 2" vent there at the lavatory.. yes?

The layout on the third floor would need to have the lavatory drain and vent increased to 2" and the other 2" vent up there is unnecessary... as long as the 4" stack on the 2nd floor goes out the roof separately.

The biggest issue I see is how you are connecting into the toilet drain line on the 2nd floor for the 3rd floor... .you can't do that.

At minimum, you will need to add a separate vent for the 2nd floor toilet...

At a maximum you will need to connect back at the 4" vertical stack and run new 3" pipe up to 3rd floor from there..?

Anyway... it can be done. When you get it all opened up pop back and let us know how we can help... OK?

MARK

Without knowing what code you fall under we're flying blind here. Milo and Growlers UPC would have you running dedicated vents on each fixture while mine is a little more forgiving and allows wet venting.. but even so my code would frown on , discharging the third floor toilet past the second floor toilet without adding a vent and the two unvented fixtures,(Laundry and tub) on the second floor plus the 1 1/2" vent venting both the toilet and the lavatory and reducing the roof vent from 3" down to 2". Code requires a 3" vent for anything over 10 fixture units. You're venting 16 fixture units. Back to the drawing board for you! To get down and dirty with specifics we really need to know what code your area falls under. Regards, Tom

All right, I am committed now. I want to get this as right as right can be so I took down the 1st floor ceiling to expose the existing plumbing for the 2nd floor bathroom/laundry. See attached: Pic~059 has the iron stack on right and the toilet flange at the end of the 3" drain at the left. You can see next to the toilet flange is the trap for the shower/tub which leads to the partially obscured 2" drain.**1 1/4" PVC pipe in bottom left of pic is connected to overflow basin under washing machine,exits out side of house**
Pic~000 shows the branches of the 1 1/2" and 2" from the 3" main drain to where they go up to the lav sink and laundry,respectively.
For code, the house is located in Massachusetts.
I will try to come up with pics of venting at the lav sink but that means tearing into wife's closet wall or the bath wall... not sure if I want to go there.
Keep the info coming any proposed solutions are welcome.
I really appreciate everyone taking the time to respond.
Rob

Rob, Lert's wait on Mark, (Massplumber) to chime in. He's the expert on Massachusetts code. If you'd add the city perhaps he can refine it down farther with local codes. Till then, Tom

Hi Rob...

Confirm that the pipe that picks up the tub is the lavatory or the laundry because it should be the lavatory pipe (2" in this case). Here, the washing machine drain/vent CANNOT act as a wet vent for the toilet and shower/tub, so if up to code this 2" pipe is a lavatory pipe that actually wet vents the toilet and the tub as well as acts as a dry vent for itself. Confirm just so we're clear...

Anyway...doesn't matter in terms of the third floor here.

Then, can you confirm that the 4" cast iron stack goes straight up and through the roof... if not, we may have another issue here... let me know!

You definitely CANNOT connect into the 3" toilet pipe the way you propose too. If you did the toilet would no longer be WET VENTED by the lavatory (or washing machine vent if done wrong).

You may be able to connect into the 3" drain right behind the toilet IF you add a separate 2" vent for the toilet (see picture), run that 2" vent upstairs until it can connect into a 2" or larger vent at a minimum of 42" from the finish floor. You will need to offset the 3" run to make room for a new 3" WYE and street 45 to pick up pipe and run it up to the third floor bathroom.

Upstairs you will run 3" directly to the toilet and 2" over to the lavatory. The 2" pipe for the lavatory will act as the WET VENT for the toilet and as a dry vent for itself (see bottom picture). Connect the 2" vent to any 2" vent you can find in the attic, or connect into the 4" cast iron OR finally, you could also make a separate penetration through the roof 2" and stub it up above the roof line between 18-24".

There is more to add... need a cleanout at the base of the stack before heading to the third floor, need to support the stack with a riser clamp or similar, etc... but will go through that when you confirm more here.

Confirm all you can... please! Let me know if all this makes sense...

MARK

Mark- First, thanks for taking the time to give me advice. Okay, you are right re: lav wet venting toilet and laundry, the lav is the 2" drain.
For the 3rd floor: everything looks straight forward, adding a 2" vent to existing 2nd floor toilet is not a problem.
Problem: the iron stack is actually a branch from the main stack in the center of the house, it does NOT continue up through the roof, it only goes as far as the plumbing for the 2nd floor bath. How much of a headache will this be? There is no space to continue it up through the roof, which is why I guess they vented the 2nd floor bath the way they did.

Alternative: If,big IF, I could move the location of the 3rd floor bath, closer to the main stack in the middle of the house. then I might be able to tie into that. It would involve cutting into the iron stack in a crawl space and putting in PVC in its place, NOT easy but doable. The cut in would be just below a existing 90 deg. Bend in the stack before it goes up through the roof, distance drain to roof~24".See pics,sorry about poor light.I would probably have to replace all the iron above that and replace with PVC up through the rough, a bit of a pain.
Also, the 3" toilet drain would need to go through 3-4 floor joists before turning to run down between joists to stack, is it legal to cut 3" holes through joists? Would plywood strapping(reinforcement) make it legal, similar to what was done on 2nd floor?
Only other plumbing on this main stack is a first floor 1/2 bath(toilet/lav).
Again thanks Mark.
Rob
I know it would be easier to get a plumber, but more expensive.I am the type of person who likes to know how things work and, if I can, do it myself, whatever that may be. I guess it is an education through doing rather than schooling, which is why I seek out people like yourself who have the expertise to give me advice.

Hey Rob...

What happens to all the vents from the 2nd floor bathroom? They must all connect together and then penetrate the roof... 2"???

If so you would still stick to the original plan of installing a new vent for 2nd floor toilet and running 3" upstairs and venting as I described (2" wet vent for toilet and lavatory), but you would connect the new 2" vent from the 1/2 bath into the 2" vent from the 2nd floor bathroom (where all vents from 2nd bath combine) by increasing the vent to 3", i.e. you would connect the 2 - 2" vents using a 3"x2" TY with a 3"x2" bushing in the bottom. This means the roof vent will need to be increased to 3" OR you could also make a separate 2" penetration for the 3rd floor bath by itself.

Otherwise I think you're all set and don't have to mess with the cast iron! But be clear... I cannot be 100% sure without being there.

Let me know if that all made sense?

MARK

Mark- All sounds good to me. I can mange all supports needed to make everything stay where it is suppose to. I should slope all drains and vents 1/4 inch per foot, right? No problem running new vent for 2nd floor bath, and then just vent the lav upstairs and I should be good to go. Increasing 2" roof vent to 3", no problem. There is already a cleanout in the crawl space where the cast iron stack goes under the house, so no worries there. Thanks for everything.
Rob

1/4" pitch per foot for vents and waste is correct!

Glad to help!

Mark- Quick question: Can I vent(new) the 2nd floor toilet straight up off the 3" drain leading to the toilet? On the picture there is a wall between the toilet flange and tub drain on 2nd floor. If I redo all the drains as you said, but instead of running the new 2nd floor toilet vent across the room, can I put a 3"/2" tee just before the 45 deg bend for the toilet flange, and run the vent straight up to the attic then tie it into the 2" vent I will put in for the 3rd floor bath?Thanks

Sure can... as long as you connect the new upstairs waste line AFTER the vent.