I'm remodeling a bathroom in a house built in 1993 (Midwest USA). Apparently the plumbers didn't add shutoff valves under the main or master bathroom sinks... I've found plenty of instructions online for how to add a compression shutoff valve, but the plumbing under the sink goes from CPVC to copper, so I'm not sure if I should really install the fitting on the copper.

My question is; Should I install the shutoff on the copper?

Or should I use a CPVC specific shutoff and take the copper off completely?

My impression is that installing a compression fitting on the copper would be easier, but I don't know if that would be up to code in this situation.

plumbing under vanity sink

1 Answer 1


I would leave the copper attached to the CPVC, if taint broke don't fix it.

I would cut it down a little so your new valves are not so high, just below the drain pipe. You can use compression, solder or push to connect valves for 1/2" copper.

I would add support for the pipes, put a piece of wood horizontal on the wall and use copper pipe standoff's or straps to secure the pipes and keep them from flexing when using the valves.

  • Good advice, especially the bracing. Last thing you want is to worry about ripping it to pieces as you try to turn that stubborn little valve 10 years from now. Commented Apr 1, 2021 at 16:04

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