How to tighten banded couplings

Old 10-06-05, 08:24 PM
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How to tighten banded couplings

I replaced a good part of the cast iron pipe in my house with ABS, as the hubs were leaking.

Where I had to join cast iron to ABS, I used neopreme banded couplings, just like my plumbing book told me to. I bought the expensive couplings, with a metal band the entire width of the neopreme.

The problem is that the outside diameter of the cast iron 4" pipe is smaller than the outside diameter of the 4" ABS pipe. When I tighten the coupling, it warps, and the metal band squishes. It looks like a dodgy seal.

Is there a trick to using these couplings? Do you have to lubricate the band so it tightens properly?

Old 10-07-05, 05:31 AM
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Cast iron is made with 3 sizes, based on wall thickness or style. Usually, the shielded ferncos (AKA Mission Clay or Mission couplers) sold at big box / hardware stores use just a generic size for home repairs, such as yours. A plumbing supplier warehouse will have dozens of sizes and combinations (sizes using different pipe material, say cast iron pipe to copper tubing or different size connections like 2" copper tubing to 3" cast iron, etc..) to choose from.

In your case, you just bought the wrong size cast iron shielded fernco. You probaby should have bought service weight size. You can measure the diameter of the pipe and match the size on the label. 4" pipe does not always mean the first 4" fernco that is found on the shelf.

Good luck with your project...probably more info than you need, but now you know....
Old 10-07-05, 01:08 PM
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Notuboo is right. I don't know how old your house is, but if you see X.H. on any of your cast iron this is another size. Lots of luck.
Old 10-07-05, 02:14 PM
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The coupling for what you need is compensated on one end with thicker rubber. When you tighten the coupling, go back and forth on the bands so it tightens evenly as the metal band will twist if you tighten one end and then the other. Good luck.

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