What is the best method to cut and cap a 4″ cast iron pipe from a bathroom demolition for insertion into a concrete sewer: mechanical insert or rubber cap with hose clamp?
Asked by Hudson Johnson 
2 months ago
Last Updated: October 22, 2024
Hey there! Check out this 4” cast iron pipe from a bathroom I took apart that’s heading into a concrete sewer. I’m thinking of cutting it and capping it off at that spot. I’m leaning towards either using a mechanical insert or a rubber cap with a hose clamp. Any thoughts on which option is better, or maybe you have a different idea? Thanks in advance for any advice!
One thing to clarify is that the exposed pipe on the right is an old drainage pipe that has nothing to do with the sewer line.
Rubber caps work just fine. Cut a section out of the iron and cap each side for easier installation.
Paul uerrero That’s a good point about capping both sides. I hadn’t considered that.
Are you thinking of abandoning the entire line? If so, it might be best to dig it out and cap the concrete line just before your next tie-in point.
Sorry, but everything else is located higher up the line.
Hey Peter, try to separate the concrete section of the drain as carefully as possible and seal both ends. This way, if part of it collapses, there will be less chance of debris getting into the working section of the drain.
Ah, so I was thinking about cutting close to the concrete, maybe within an inch? Can you think of any reason why we shouldn’t use a product like this?
Sure! Just to clarify, you would like me to provide you with the gently rephrased text only, correct?
Have you thought about using silicone alongside it? I couldn’t find any information on the website about whether it’s approved for burial. I do know it’s safe to use in permanent situations.
If you don’t know what’s inside the current concrete pipe, it might be a steep slope. I wouldn’t recommend using that plug shown above for burying directly. Personally, I would suggest cutting the concrete pipe and capping it off. If the cast iron pipe is not in use anymore, just leave it be. The goal is to prevent any debris from going down the line.