I'm replacing a shower that has a 1.5 inch drain with one with a 2 inch drain. PA code allows 1.5 inch shower waste pipe. Even though everyone advises replacing all the pipe with 2 inch (which I would like to do), the 3x1.5 Y where the 1.5 inch pipe attaches is essentially inaccessible and so I was going to leave in the 3 feet of 1.5 inch line.
Is it better to reduce from 2 inch to 1.5 inch between the drain and trap or somewhere between the trap and the Y? And why is that? Thanks. (BTW, it's all PVC.)



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adding a ABS 2 x 1 1/2 reducing coupling is what I would add using a 2" shielded transition coupling. Then run 2" for the rest of the trap arm, p trap and tail piece. Add support at transition from steel to plastic as needed. Leak check.

[www.fernco.com]

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Is there a reason you recommend a shielded transition coupling rather than a standard simple PVC 2"-1.5" coupling? There is no stress on it.

ANY non-eccentric, (concentric), connector between an upstream horizontal pipe and a smaller downstream one WILL create an obstruction. Either make the reduction on the vertical pipe above the trap or use an eccentric coupling.

ditto

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Got it. Thanks to you all!



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