Supporting vertical vent pipe

[Calavera]

Hello All,

I have an old cast iron pipe that is cracked. the crack leads up to a t-connection between the line coming out of my kitchen sink and a vertical vent pipe. Here is a picture:

As you can see the pipes sits a few inches away from one stud and about a foot from the other which is hidden from view by the wall. i have replaced most of the line coming from the main waste exit from the house to the point in the picture, so my intention is to continue replacing up to the cracked pipe. so here is my problem. I figure I will have to have to replace the entire t-joint(if not i'm luckier than i think), but that will mean cutting the vent pipe and the pipe from the sink. this doesn't seem like that big of a deal except, i am not sure how to support the vent pipe. i've read about riser clamps, but the clamp would have to be pretty long to make it to the "hidden" stud. or, if i can connect the t-joint to a pvc pipe without cutting into the pipe for the kitchen or the vent pipe. how do i support the weight of the vent pipe then as well? Can anyone give me some advise on how to continue?
Thanks in advance-
Todd

 

[Jadnashua]

While you could go between the studs to provide the clamp and support, if you can get above the header, you can add a smaller clamp, and the 'wings' of it would just rest on the header, and the lower portion would then be suspended.

 

[Sponsor]

 

[Calavera]

I see, so just get up in the attic and secure it at that point, right? And I would still use the riser clamp?

 

[Jadnashua]

Yes, you'd install the riser clamp so that when tight, it is right up against the top of the header drilled for the pipe to pass through. Then, since the clamp has wings on it, those prevent the pipe from falling, assuming you've tightened it properly. No need to bolt it to anything unless you want to prevent it from rotating.

 

[Calavera]

Thanks for the advice. Now I am trying to figure out the T connection. I believe that the top and left pipes are galvanized wrought iron and the bottom one is obviously cast iron. the size of each has the appearance of being different but i've read up on the standard of each pipe. I measured the circumference of each and calculated the diameters. It looks like it comes out to this:

Vent:
~ 7 ½ inch circumference = 2.38 inch diameter = 2 inch pipe

kitchen:
~6 inch circumference = 1.91 inch diameter = 1 ½ inch pipe

the one to waste is cast iron:
~7 1/8 inch circumference = 2.26 inch diameter = 2 inch pipe

so if i replace the connection between the three, will a fernco rubber coupling be sufficient? are my calculations correct about final pipe sizes, ie. is a 2 inch, 2 inch, 1 1/2 inch coupling the correct one to get?

Thanks again in advance.

 

[Calavera]

I've just looked and fernco doesn't have a 2 x 2 x 1 1/2 reducing tee connection and my quick look doesn't pull up anyone else that sells it. i supposed i can just try and remove the cast iron pipe then no hub couple pvc to the original connection. anyone else have any other suggestions. I know there is a pvc version of the reducing tee also. Which is my best option?

 

[Cacher_Chick]

I cannot see what kind of structure you are working on, but I can't help but wonder how much trouble it would be to replace the entire stack with PVC? If it's a single story, it might take less time that fixing what is there and be a better long term solution.

 

[Calavera]

I finally tackled this project this weekend. I extremely meticulously cut and chiseled away the lower pipe from the t-joint. I got lucky enough that the t joint came out intact. i no-nubbed pvc down from there. I didn't mess with anything above.