Vertical Cast Iron Support

[KiviP]

Hey everyone,
I need to add a tee to my vent stack to accomodate a new sink. Current sink horizontal vent arm is at 36 which is too low and I need to bring it up to 42 to be above the 6 inch flood rim rule with my ne2 vanity. Old vanity was mounter at 30. New one will be around 34 ish. I already braced it but I was wondering if this is good enough.

I am going to cut below the strapping and transition to ABS. I would say I have 2 to 3ft of pipe supported by that strapping. Would it be ok should i just cut it all out and put a new pipe through the roof? In that case do I need solid core PVC and then paint it?

 

[Tuttles Revenge]

you've likely got about 50-75 pounds up there so the strap would be strong enough to hold it temporarily. A concern I have is that with only strapping on that small section through the roof it might spin the pipe like on a trapeeze and cause a leak at the roof flashing.

Is the stack plumb vertical or is it angled beyond plumb, just looks angled to me. If its angled I would get some wood framing to contact the stack to bear the weight of the transition.

 

[Sponsor]

 

[KiviP]

you've likely got about 50-75 pounds up there so the strap would be strong enough to hold it temporarily. A concern I have is that with only strapping on that small section through the roof it might spin the pipe like on a trapeeze and cause a leak at the roof flashing.

Is the stack plumb vertical or is it angled beyond plumb, just looks angled to me. If its angled I would get some wood framing to contact the stack to bear the weight of the transition.

Stack is plumb. Those are rafters and the picture can be a bit misleading visually. I have a 3 inch riser clamp but there is really not much room to put it since the left side is a bit too close to rafter. Picture from the other side.

I am only intending to leave like 2-3ft above the cut. Is that really 50 to 70lbs? I thought CI is like 7 to 10 pounds per ft
I have the concern about it moving and causing a leak at the roof as well. Not really any great place to put support around

 

[Tuttles Revenge]

A quick search shows 4" at 13.5 pounds per foot. So 25-50 pounds if its 2ft and light or 3ft and heavier than normal. I'd plan on it being heavier. I think your straps will hold the weight, tho it might shift. Depending on roof construction sometimes the tar used to seal it will hold if the weather is cold, but will melt when its hot. Or its just up in a lead / rubber boot and the roof is not doing any support.

How taught are the straps you have up there now? If they're super tight then maybe you wouldn't get any deflection. You could strap a lenght of L metal to the stack that spans from both the hubs of the tee and up above the point you need to fill in your new tee and create a spacer/shim that is plumb and strap that too the upper section to keep the leftover chunk from moving.

 

[KiviP]

A quick search shows 4" at 13.5 pounds per foot. So 25-50 pounds if its 2ft and light or 3ft and heavier than normal. I'd plan on it being heavier. I think your straps will hold the weight, tho it might shift. Depending on roof construction sometimes the tar used to seal it will hold if the weather is cold, but will melt when its hot. Or its just up in a lead / rubber boot and the roof is not doing any support.

How taught are the straps you have up there now? If they're super tight then maybe you wouldn't get any deflection. You could strap a lenght of L metal to the stack that spans from both the hubs of the tee and up above the point you need to fill in your new tee and create a spacer/shim that is plumb and strap that too the upper section to keep the leftover chunk from moving.

Oh, this is a 3 inch stack so should be a bit lighter than the 4 inch.

 

[Tuttles Revenge]

Oh, this is a 3 inch stack so should be a bit lighter than the 4 inch.

Ahh... gotcha.. We never see 3" cast iron stacks.

 

[KiviP]

Ahh... gotcha.. We never see 3" cast iron stacks.

All of my stacks are 3 inch. Only 4 inch drain lines I have are for a short run for the toilet. At most 3-4 ft each run

 

[KiviP]

Actually, would be ok to run a new 2 inch vent stack from the roof that ties into the existing horizontal 2 inch steel pipe? Not sure if that is legal or not. It will be less work than replacing the existing CI above roof. I have a roofer who would put a new boot in for 100 bucks

UPDATE: never mine. I think this is actually dumb

 

[Tuttles Revenge]

Yes, a new roof penetration is ok.. But I prefer to keep the number of holes in the roof to a minimum.