What are the general thoughts on those service weight gaskets/donuts when connecting PVC to cast iron? I need to hook up a piece of PVC pipe to a cast iron pipe with a bell. This in something that will be buried under the slab for a bathtub installation. I believe my options are to keep the bell and use a SWG or cut the pipe to remove the bell and use a coupler. The latter requires a bit more work. Are those gaskets more prone to leak compared to the couplers?
Service Weight Gasket/Donuts: General Thoughts
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Jadnashua
Retired Defense Industry Engineer xxx
Either should work if you get the right size. Note, while the ID of the CI pipe is standard, the actual size of the bell is not and can change from one maker to the other, and over time. Fernco, one of the major suppliers of the donuts, makes LOTS of them. Get one too small, and you'll not get a good seal. Get one too large, and you won't be able to cram the pipe in there...just like Goldilocks...it needs to be just right. You really need to measure to ensure you're getting the right one. The OD for a coupler in that case, might be easier, just make sure you don't have raised markings on the outside of the cast where you want to make the seal! It needs to be smooth.
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I've had no problems using the gaskets in the hubs. It makes for a nice job.
I have looked at Charlotte's and Fernco's web sites for their gasket products. I know I will need a 2"x 2" since the bell has around 3" in its internal diameter. However, like you guys noted, I need to pay attention to the accuracy of the measurements. Charlotte has a regular type and a extra heavy type for each product size with variation in the 16th and 32th of an inch. They have one with a molded bead that is supposed to fit the lead groove inside the bell. I was considering getting one of those but have not been able to find them even online. The big box stores carry Fernco and American Valve. Is there a brand normally found in local hardware store that I am not aware of and might even be a better option?
The big box stores carry them, and all the plumbing supplies. I like to carry at least two different ones heading out to a job, as sizing can be different. You can return what you don't use, or in my case, it sticks around for the next call I do like that.
Just to add some additional thoughts to this discussion for future reference, would it be a good idea to add a couple of beads of plumbers putty to the ridges of the donut/gasket seal to reinforce the joint against leaks?
No plumbers putty.
Liquid soap to help slide it in, or if you really want to add something, Silicone (I've nevere had to use it though)
Liquid soap to help slide it in, or if you really want to add something, Silicone (I've nevere had to use it though)
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