# Pex on Shower/Tub Rough In



## AlphaPilot (Aug 6, 2012)

Looking for clarification on the topic of using PEX instead of Copper with showers and tubs. The argument I hear is the ID of Pex is less than copper with both 1/2" items. Is this only a problem with tub/shower combos? And does ProPEX make any difference, or does the argument still hold true? I hear that when drawing a bath the shower head drips due to too much restraint. Is there any other issues?


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## joecaption (Nov 30, 2011)

Yes PEX is slightly smaller.
Use 3/4" for the supply's and you'll have about double the avalible flow as 1/2" copper.
I have not used copper for at least 10 years.
Far faster, cheaper to use PEX.


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## Yodaman (Mar 9, 2015)

The only issue with PEX on a tub/shower valve that I am aware of is the restrictive flow into the spout just as you described. I learned of this first hand many years ago.

PEX per say isn't the problem, its the ID of 1/2" Pex that causes the back pressure.
I solve the problem by using 3/4 PEX on the spout drop. I buy 2 adapters that I normally order thru Pex Supply. 1/2 npt x 3/4 pex straight, and a 3/4 PEX to 1/2 NPT drop ear.

Here is a rough in I did a few days ago.


View attachment 345969


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## Jim F (Mar 4, 2010)

You could use 1/2 inch copper for the spout drop and PEX for the shower and that would give you lower resistance in the spout and prevent the water from being diverted up to the shower head when the spout diverter is open.


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## TheEplumber (Jul 20, 2010)

The valves I buy from a plumbing supply house have pex inlets and sweat outlets to the tub and shower. I never run pex to either outlet for 3 reasons- 
Size reduction of pex to the tub will cause the shower to dribble on some valves.
Second reason is I like the rigidity copper gives the completed rough in assembly
Third reason- I'm old school and like to solder copper....


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## Yodaman (Mar 9, 2015)

TheEplumber said:


> The valves I buy from a plumbing supply house have pex inlets and sweat outlets to the tub and shower. I never run pex to either outlet for 3 reasons-
> Size reduction of pex to the tub will cause the shower to dribble on some valves.
> Second reason is I like the rigidity copper gives the completed rough in assembly
> Third reason- I'm old school and like to solder copper....




These three hole drop ears solve the rigidity issue. The original 2 hole drop ears would allow some movement. These 3 holes are supper spot on tight.


1/2 NPT x 1/2 Pex 3 Hole Drop Ear on the shower riser.









A typical shower head runs about 1.5 gpm, well within the capacity of a 1/2 Pex inch line.

On the tub drop, running 3/4 Pex, which is larger than 1/2 copper ID solves the back pressure and dribble issue. Just need adapters to up-size to 3/4" Pex. I use the off-the-shelf Moen valve, which comes with 1/2" male outlets.


1/2 NPT x 3/4 pex drop ear for the tub drop













1/2 NPT x 3/4 PEX straight on the valve outlet to tub drop


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## TheEplumber (Jul 20, 2010)

@Yodaman, to each his own. Mine will always be rigid copper pipe. Those adapters wouldn't work on the valve connection system I purchase anyways
http://www.moen.com/products/MPact/...X_connection_includes_pressure_balancing/2580


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## AlphaPilot (Aug 6, 2012)

Thanks for the replies, guys. Truly helpful with the photo and I'm happy to say I understand all the terms. Lol.

I wasn't sure if my ProPEX (Pex A) would be okay to run 1/2" or not for the tub spout because I know ProPEX has bigger ID than typical crimp Pex (B or C I can't remember).

I definitely would go for the all pex option because as a DIY job, I know I wouldn't trust my soldering enough to cover it up unless I ran water through and tested it, which is a hassle. I love the ease of the drop ears, and I make my lines plenty solid with clips and blocking. Now if only my order could arrive here as fast as Amazon Prime!


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## Yodaman (Mar 9, 2015)

TheEplumber said:


> @*Yodaman* , to each his own. Mine will always be rigid copper pipe.



We wouldn't dream of trying to persuade an old salt like you Eplumer. :wink2:

Just re-iterating, to anyone interested, that there is a viable PEX solution on the tub spout drop.


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## Yodaman (Mar 9, 2015)

CTSNicholas said:


> I wasn't sure if my ProPEX (Pex A) would be okay to run 1/2" or not for the tub spout because I know ProPEX has bigger ID than typical crimp Pex (B or C I can't remember).



I doubt it would large enough, the propex I.D. is only .028 larger than the standard
http://www.uponorpro.com/~/media/Ex...uaPEXProPEX_Compare_C274_0211.aspx?sc_lang=en




CTSNicholas said:


> I definitely would go for the all pex option because as a DIY job, I know I wouldn't trust my soldering enough to cover it up unless I ran water through and tested it, which is a hassle.




Regardless of which method you run, doing a quick functional test is as simple as screwing in a couple 1/2 npt plugs into your drop ears, then turning on the stops.

Better to find a problem while everything is opened up, then to find it later. People have missed crimping the ring on occasion. :biggrin2:


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