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Senior Member


Saturday, June 20th 2020, 8:00am

Plastic threaded fittings shrinking until they pop out...

Have a pump with threaded inlet and outlet. Cast iron housing I think - some sort of steel. A few years ago I had the PVCinlet thread creep over time until it popped out. It had some side force on it from the weight of the pipe so put a support a couple feet from the pump on inlet and outlet. Just had the poly pipe insert fitting on the output do the same thing. I could use a steel fitting on the output and could use galvanized on the input too. Is the cast iron rust scale in the threads pushing the threads smaller. Wondering how this is happening and a good solution.
illinoisjim has attached the following file:

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