Replacing section in 4" vertical Cast Iron pipe

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AdnanInNY

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Hello All

I hope someone can give us some helpful advice on a situation we have.

Our upstairs bathroom didn't have any fixtures when we bought the house 3 yrs ago. After putting in a toilet, tub and vanity in it, we found out the cast iron stack is badly cracked. The crack goes all the way from the floor of the downstairs bathroom to the hub which connects the the piping for the upstairs bathroom. So this will have to be changed.

The piping of the two bathrooms is:
Downstairs toilet has 4" cast iron pipe going straight down to basement and into the ground.

Upstairs toilet has 4" cast iron pipe going straight down to basement and straight out the roof. This pipe is connected in the basement with an elbow and 5 ' pipe to the pipe going into the ground.

WHERE I NEED HELP
If I were to cut out that 7' - 10' cracked cast iron pipe and replace it with solid wall dwv pvc, would the pvc be able to support the 10' cast iron pipe which will sit on top of going out the roof. The other alternate would be to put pvc all the way way up before it shoots out the roof.

Supporting the pipe, I got those 4" riser clamps from Home Depot, but they are a little too big for the pipe, can I cut open that Fernco coupling and wrap it around the pipe and then riser clamp. In addition I will also nail a 2 x 4 under the toilet elbow for extra support.

Thanks
 

Dj2

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1. Gain wall access to be able to cut the CI pipe and remove it. Might as well go with PVC all the way to the roof and beyond. Use a recip saw with CI blade.

2. Use a Frenco (or other brands NO HUB COUPLING - the one with the metal support and 2 clamps). Make sure one side fits CI and the other fits PVC.

3. Attach the coupling to where you cut the CI, after cleaning the cut well.

4. Build the PVC up from there. Secure the pipe to code.

Go to YouTube and watch some demos before you start.
 

AdnanInNY

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Hi dj2. Thanks for your reply.

For cutting the cast iron pipe I bought the diablo carbide thick metal reciprocating saw blades. They are a beast. Right now buy 1 get 1 free for the 6 inch at Home Depot. I got 3 packs, will buy a few more. I also have an angle grinder but scared to use it.

Would this work?
Supporting the pipe, I got those 4" riser clamps from Home Depot, but they are a little too big for the pipe, can I cut open that Fernco coupling and wrap it around the pipe and then riser clamp. In addition I will also nail a 2 x 4 under the toilet elbow for extra support.
 

Dj2

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I use an angle saw to cut CI pipes whenever I don't worry about access. The sparks that fly cause no damage when you use precautions. However, in a wall cavity, a recip saw is better.

Cutting and modifying a Frenco coupling is not a good idea. Better find the right size for the job.
 

Terry

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Old cast iron is copper sized. It will be 4-1/8"
To fit that, you need copper sizing on the no-hub clamp where it meets the old cast, and then plastic sizing on the other side.
I have also used copper x no-hub cast for that.
 
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