I need to add a 4" riser clamp to a 4" cast iron pipe.

How hard can I torque on the nuts? Can you crack the pipe using one of these clamps?

Also the pipe comes out between 2 floor joists. I was thinking I would easier rest the sides of the clamp on the floor joists or add 2x4 cross wise and rest the clamp on the 2x's. I assume there are no screws needed.


What is the proper method for using these?

i can't imagine you could crack the cast. but, if there is a concern, cut a couple of strips of rubber (like rubber roofing) to line the hanger with.

no concern other than its old cast iron... I figured it was brittle.

So you guys torque them up till they nuts wont go further?

No dice. I cant fit a support board where its needed to span the joists. I would have to notch a truss to slide it into place.

My other option is only having one side/ear of the clamp supported but I figure that would be worthless?

So I have a 60 year old one story vent (maybe 10') It has strapping at the base of it and there is a waste arm/tee in the vertical vent.... can I depend on that if I am cutting into the lateral portion of the drain?



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is there any possibility of getting a prop or two under the lowest vertical hub?
even two pieces of strapping cut to the right length and angled under the hub will do the job.

The lowest vertical hub is in a wall. From the basement I only have access to the 90 where it turn up to the vent. As mentioned, there is strapping there (wrapped around the 90 and secured to a joist. The horizontal portion spans about 8 feet and it too is strapped to the joists in two spots before that too turns vertical and out of the building.

I had 2 plumbers look at it, including the one doing the work and he said don't worry, its not going anywhere I do this all the time! But contrary to that everything I read online about cutting into cast iron calls for riser clamps.

Should I just trust in my plumber (and his insurance!)?

When you support vertically, isn't the weight stressing the joints?



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there are more types of hangers than you can imagine.
anything here you can use?

You torque them until they are tight, regardless of whether there are still threads showing or not.

If "one side" of the clamp cannot slip down, the other side can't either, even if it is not supported by a board.

quote; I had 2 plumbers look at it, including the one doing the work and he said don't worry, its not going anywhere I do this all the time! But contrary to that everything I read online about cutting into cast iron calls for riser clamps.

I have NEVER had to use a riser clamp when cutting into cast iron. Trust the guy doing the work and quit second guessing him.

Not likely because everything there is for a horizontal line, not a vertical riser.

he said he had perforated strap holding the horizontal pipe. I thought to get rid of the strap and use a real hanger. (on the horizontal)

When you support a section of vertical pipe, are you only supporting the pipe between hubs/joints?

Thinking if a vertical pipe gave way, wouldnt the joints below the clamp bear the stress... pull apart?

Like in my case, where I intended on placing the riser clamp there is only about 16" between a joint and where it exits the roof line.... below that joint there is 10'.



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that would give it stability from side to side but no vertical support below. there is a supprising amount of strength to a properly packed and poured and caulked lead joint.

So then proper support of the vertical stack is always depended on how many joints there are?

So what if you cant get to the next closest hub in the attic... are you guys breaking walls each time you cut into the system?

FWIW: Now I have the riser clamp on the short section of pipe in the attic resting on 1 2x4 spanning the joists (which I assume is worthless?)....

I also have a galvanized branch tee'ed off that stack presumably going thru studs and the strapping at the 90 at the base of the stack. The 8' horizontal portion is now strapped in 3 spots as well.

My OCD getting the best of me....

where is the plumber you referred to while you are on this ridiculous journey to support the pipe?