# Best PEX tubing size for shower valve?



## Studly (Feb 27, 2009)

I'm going to remodel our shower, and will be putting in a new valve and trim (no tub, shower only). Currently, the plumbing is copper, but I want to change it out to PEX in that shower. What size PEX is typically used in the hot and cold water supply lines to the valve and from the valve to the shower head? I don't have the wall opened up yet so I don't know the size of the copper that's in there, but if the shower head only flows at 2.5 GPM, would anything more than 1/2 inch pex into the valve and to the shower head just be overkill?


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## joecaption (Nov 30, 2011)

Most likly it's gong to be 1/2" copper.
1/2 Pex will work fine, but 3/4 will give you almost 50% more avalible CFM.


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## Studly (Feb 27, 2009)

joecaption said:


> Most likly it's gong to be 1/2" copper.
> 1/2 Pex will work fine, but 3/4 will give you almost 50% more avalible CFM.


Yeah, I know that to get the same flow rate, in general, you want to upsize the pex one size so it flows the same as copper (3/4" pex=1/2" copper). Originally I was going to go with 3/4 pex into and out of the shower valve and then I read that many others, when plumbing their new shower with pex from scratch, just use 1/2" pex for the whole run to the shower. I figured that must be because of the fact that most shower heads these days are limited to 2.5 GPM or less, so 1/2" pex is probably more than enough for that flow rate (unless you have multiple shower heads in your shower)?

On the other hand, the cost difference between 1/2 and 3/4 pex is so minimal for the short runs I'll be doing, maybe I should just use 3/4 all over?


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## joecaption (Nov 30, 2011)

That's what I'm thinking. Much easer then going back and having to change it when the little woman comes home with one of those silly rain showers and it does not work.


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## Ghostmaker (Mar 2, 2013)

1/2 inch is all you need for a shower head and a hand hold. The 2.5 gpm flow rate is now built into the valve itself.
Make sure you get a pressure balanced temp control valve.


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