View Full Version : iron pipe wet vent okay?

10-02-2005, 09:36 AM
We are planning to finish out our third floor with some dormers and a new bathroom. The house originally had just a first and second floor bathroom, and all the plumbing is old cast iron.

The first floor toilet has a 2" vent coming vertically out of the behemoth iron fitting, and it goes up along the 4" stack. The 2" vent pipe picks up the floor 1 lav /tub vent loop just below the second floor and continues up to join with the floor 2 lav/tub vent and connect to the 4" stack just above the second floor ceiling in the attic. In the photo, you can see the main stack on the right, the floor 2 toilet connection out the back, and the second floor 2" lav/tub drain on the left. The first floor vent is on the left looping around the second floor lav/tub drain.

The second floor iron fitting is different in that it doesn't have the 2" toilet vent hub built into the cast iron right beside the stack, but the lav/tub drain joins in right at the same height as the toilet connection. Two plumbers have looked at it, and one said it would be okay since the tub/lav drain has a 2" vent and this would vent the toilet. The other said that the inspector would never let it pass, and it would have to be replaced with pvc to vent the toilet. The price to replace it with PVC was huge, probably due to the effort required to chop out the iron. I don't want to go to the effort though if it is okay the way it is, and would pass inspection.

If I were to do this myself, I would chop out the second floor iron behomoth just below the bottom flange and use a 4"x4"x3" sanitary tee with a 2" side inlet (esterbrook?). I can use a 4" hubless connector on the main stack, and tie the second floor tub/lav drain into the 2" side port. I would use a new toilet flange in the floor, then a 90 into a 3"x3"x2" wye on its back and then into the stack tee. On the wye, the 2" vent would be rotated about 45 degrees up from horizontal. From there I can just clear the corner of the floor with a couple of street 45's and go vertical to join up with the first and second floor 2" vent and both will be extended to join with the main stack above the third floor bath.

Sorry for being long winded. Does this sound reasonable or am I way off track?

10-02-2005, 12:32 PM
It taxes the brain to try to follow how you would install it. but to get an installation that an inspector would approve, you would need a "behemoth" fitting like the one at the first floor installed at the second floor. The all the vents would have to be revised to accomodate it, and the connection into the stack at the 42" level would be discontinued and reinstalled at the 42" point above the floor in the third level.

10-03-2005, 06:30 PM
Thanks for the reply.

I guess that the original fitting is really not vented correctly. Assuming that I can get the thing cut out, I would like to replace it with PVC. I made up a drawing of what I want to replace it with (black pipe is the original iron). I haven't shown the closet flange or pipe stub, but they would go on the left side into the 3" 90. I also haven't shown the clamps, but the tub/sink drain on the right would get cut off and clamped into the new fitting, as would the stack coming up from the first floor at the bottom. The vent would continue up and pick up the iron tub/sink vent and then up to the third floor where it would join into the stack at the 42" level.

Does this piping look reasonable? I am concerned about the meandering three 45's for the toilet vent, but that's the only way I can clear the corner of the bathroom floor. Does the code require a long sweep 90 just below the toilet?

Thanks for any and all feedback.

Dunbar Plumbing
10-03-2005, 07:07 PM
That 3X2 wye is reversed in the direction it should be and I believe that side outlet tees are illegal. You can drop a wye under that tee to catch what you need to. What kind of software did you use for that drawing?

10-03-2005, 07:39 PM
That 3X2 wye is reversed in the direction it should be and I believe that side outlet tees are illegal. You can drop a wye under that tee to catch what you need to. What kind of software did you use for that drawing?

Yeah, I thought that might be bad since it is pointing upstream. I can't possibly pipe it with the wye the other direction though. Can I use a side outlet tee or a sanitary tee for the toilet vent instead of the wye?

If the 4x4x3 san tee with a 2" side inlet is illegal, I could go with a wye under it.

The software is solidworks. I use it mainly for work to model mechanical stuff, but it works pretty good for pipe too.

10-03-2005, 10:45 PM
Most plumbers will have a waste stack that they will wye off of.
As you have noticed, there really is no room to vent how you have it above.
Fittings must be the right way, not just anyway because it's easier to do.

So.......start thinking this way,
The stack goes up through the floors.
On each floor, you will wye off of the stack for more fixtures.
The fixtures will have santees on the vertical with the vents going up.

The vents can be tied back together at 42" for each floor.
You may wind up with two vent stacks and one waste stack that way.
If it's night right when you cover it, you could be sorry.

Yeah, well that's a given.

10-04-2005, 12:33 PM
Thanks Terry, although I have seen that diagram several times, it wasn't until I read what you wrote that it made more sense.

I revised my picture to what I think is a better arrangement, and I think I can still squeeze it into the space I have. I show a main stack wye hooked into a sanitary tee with a 2" horizontal side inlet used to take the tub/sink drainage. This tee takes the toilet waste at the 3" horizontal inlet. The two inch vent on top vents the toilet.

There is a separate 2" cast iron vent pipe that loops around from the tub and sink and connects back to the vent stack at the 42" level (not shown in picture). I think I can simply wye the toilet vent together with the tub/sink vent at that point. From there they would continue up to the third floor and connect to the main stack at 42" above the third floor.

If this piping looks like I am on the right track, I still have two concerns. First, are the 3" sanitary tees with a 2" side inlet legal in MA? They seem to have a lot of them at the local store with the orange logo... Second, does the tub/sink drain coming in from the right need to be a long sweep?

Thanks for all the input

10-04-2005, 03:39 PM
I would drop the 4x3 wye lower on the main stack, and add a 3x2 wye for the tub below the santee for the toilet.

A good rule of thumb, would be to add waste lines below the venting santee.

waste on the horizontal requires long turn or 45's
Vertical to horizontal requires long turn or 45's
When waste goes from horizontal to vertical, you can use a med bend or a santee.

10-06-2005, 07:35 PM
Thanks Terry, I think it makes sense now. I included the revised picture below just in case someone is interested.