PEX or copper between valve and tub spout

i have heard that using PEX pipe between the tub/shower valve and the tub spout may be a bad idea, as it may cause water to go out the shower when unwanted. not sure why, unless the elbows for PEX being on the inside cause a restriction.

also do newer valves account for this in any way ?

trying to avoid soldering (i.e. using copper).

planning to use PEX from the valve to the shower head.

Also have heard that the distance from valve to tub spout s/b between 11" and 18". is this just about aesthetics or are there technical reasons ?

thanks.

mike

1/2" copper verses 1/2" PEX have the same external dimensions, but the internal dimensions are different PEX pipe walls are thicker, thus smaller and lower flow capacity. Any restriction to the tub spout will often be enough restriction to cause it to slowly backup in the showerhead riser, and dribble out there as well. Plus, there isn't a good way to attach any of the tub spouts to PEX. They typically are either a slip on or a screw on connection. You can't anchor the PEX, so your spout would move and the connection would be a problem. PEX to supply the shower valve is okay but not for the tub spout.

thanks for all the responses; much appreciated. i will look into those drop ears - i'm a bit leary now of the PEX, after running into a guy at the home depot who had the shower rise issue, and the Delta help desk told him to go back to copper. tried to get some info from Moen, but couldn't get thru. i will look into those drop ears.

The problem with PEX is the pipe between the valve and spout, NOT the fittings or loose ell. A drop ear elbow is need regardless of the material, but it will not eliminate the back flow problem if you use PEX. Maybe the customers of the pros who "use it frequently" only use the tub as a shower so they do not have the problem.

I’m glad I caught this. Shower pressure is a big thing for me. That’s why I’m running three-quarter inch PEX up from the basement to this new second-floor bathroom. I have no problem sweating copper joints, so this is definitely the way to go for me. I have a feeling that the tub spout will be stronger with real copper pipe instead of the PEX stub out I was initially thinking about. Especially because my tub spout is a slip on connector. So PEX up to the valves (3/4 inch almost all the way until the last few inches) and copper from the valve to shower and tub spout seems to be a pretty clear solution for water pressure. Unless I decide to just go for 3/4 -inch copper for the valves, too. I kind of wonder if the 6 inches of half-inch PEX will restrict flow even a bit.

You can't use PEX for a tub stub out either. A slip spout needs copper.
PEX fittings also restrict quite a bit and do push water upward to the shower head.
I had to open a wall up behind someone else's work when they had run PEX to the drop ear 90 on the tub spout. It was pushing water up to the shower head when filling the tub. I cut the wall open and changed it to copper to fix the problem. And then someone else came in to fix the wall that I had cut.





Delta makes a valve with the tub drop already soldered on.

1/2" PEX with one shower head would work from a supply situation without reducing your effective pressure, but if you used that as supplies to a tub, you might notice it takes longer to fill it...but, as has been said, using pex to run to a tub spout is bad news. I disagree with the OP's install diagram that says galvanized is acceptable...IMHO, while it can work, it WILL eventually rust...use a brass nipple if it is threaded or a copper stub with a fitting soldered on. Using PEX to a tub spout would also mean there's no good way to stabilize it...PEX is just too flexible.

And here are the Delta instructions.

Speaking as a DIYer, if the shower valve has threaded connections (I assume it does or pure PEX wouldn't have been an option) I wouldn't be too nervous about this being your first experience sweating copper. Practice a bit, then solder the threaded end onto the copper, attach it, and solder the elbow or drop ear onto the other end depending on your situation. Just keep the valve above what you're soldering so you don't drip solder into it. Worst case is you totally mess it up and have to unscrew the copper from the valve, throw it away, and try again.

Even if it has the combination threaded/solder connections, if you haven't done soldering before I would use the threads. Soldering 1/2" copper fittings is really easy. Brass valving is a bit harder---I've done quite a bit of soldering and the one joint failure I had in my current project was a tub valve.

Bruce

There exists a 3/4" PEX x 1/2" Female Threaded Drop Ear Elbow. This would seem to overcome the absolute injunction injunction using PEX on the way to the spout.

http://www.pexuniverse.com/3-4-pex-x-1-2-drop-ear-elbow

This is not for expansion fittings, but rather for compression or clamp.

Know this is ancient thread. I will probably be doing as Brucel mentioned except don't like having make sure get threaded ends so bottom elbow lines up perfect. If need tighten a tad then the elbow ends up mis-alligned. Thus really like PEX adapter fittings. Recently, saw somewhere else that Delta had said could use 3/4" PEX as drop which would do to a drop ear el then metal nipple to spout. I am using 3/4" PEX lines into the Delta valve using the 3/4" PEX x 1/2" female threaded adapters. Same up to the shower drop ear as posted by Reach4. Originally, planned same down to tub but had decided copper. So the Delta approval caught my eye.

I'm using the 17T cartridge to get as much flow as possible to fill the tub thus larger 3/4" PEX which is pretty close id to copper. Have removable panel for full back side access plus open basement area access/visibility to catch any future leaks (hopefully none but plan for worst).

Since 3/4" PEX slightly larger inside diameter than 1/2" copper or iron pipe (per printed instructions) seems that it would prevent the back pressure problem that "standard" 1/2" PEX would which is what assumed with directions provided that state not to use PEX as drop for tub spout. If my understanding is correct, the valve opening to the tub is larger than the shower which allows more water combined with the smaller 1/2" PEX is really the issue causing the backflow problem. Thus seems that using the 3/4 PEX would solve that part of the problem (and why Delta would suggest/approve) as long as used metal to the spout itself. My tub spout can accept 1/2" slip or threaded as well as threaded 3/4" pipe so am not limited there in any regard.

Since the drop ears for the pipe to spout would be secured doesn't seem what type pipe used for the drop matters as long as not size restricted. Logical?

If there is a restriction in the PEX fitting to 1/2" there would be water pushed upward to the shower head when filling the tub.
PEX is coupled using an insert fitting. It will restrict at that point unless it's a 3/4" and not to 1/2". Copper is coupled using a coupling that fits over the pipe. Big difference.
Everybody is allowed to make a mistake once. Since you have a wall access you can fiddle with it if needed. For most people, it's cutting the wall or tile to make the fix.

Reach4 said:

There exists a 3/4" PEX x 1/2" Female Threaded Drop Ear Elbow. This would seem to overcome the absolute injunction injunction using PEX on the way to the spout.

http://www.pexuniverse.com/3-4-pex-x-1-2-drop-ear-elbow

This is not for expansion fittings, but rather for compression or clamp.

Click to expand...

This 3/4 PEX drop ear to 1/2" NPT works without issues. I installed it and have no issues. There is no restriction in the fitting (I got mine from Supply House). Good pressure all around.

I have 1/2" PEX to the DELTA tub/shower valve (nothing special from Lowes), and 3/4" PEX going down to tub spout elbow (1/2 brass nipple out to the tub spout) and 3/4" PEX going up to the shower spout elbow.

Using Uponor fittings should be an alternative solution as by design, although the drop ear elbows are insert, the pipe is expanded so all the fittings are full flow.

..unless I’m missing something

-TC

YES, you're missing something. The PEX is much smaller than copper on the inside. Also the fittings are a further reduction in size. If you run PEX to a tub spout, it will force water to the shower head. Read the instructions carefully for your valve and you will see the warnings.
Terry Love

Sbikeguy said:

Using Uponor fittings should be an alternative solution as by design, although the drop ear elbows are insert, the pipe is expanded so all the fittings are full flow.

..unless I’m missing something

Click to expand...

1/2 inch PEX pipe, even without considering the fittings, is smaller ID than 1/2 inch copper. Yes, the Uponor F1960 fittings have bigger ID than the common F1807 or F2159, all PEX fittings of a given nominal size are smaller than copper fittings.

I know this is an old thread, if should post elsewhere please let me know.
Installing a delta shower valve during remodel (multichoice R10000 UNBX). Existing pressure in the house isnt terrible, isnt great either.
Ran 3/4" Pex-B (crimped) for both H/C supplies to valve, same 3/4" pex up to shower head and have already sweat 1/2" copper drop 18" down to tub spout. Intend to pressure test, and may actually try real world use test once tub is buttoned up but before board installed for tile, so if my setup is off base i do have time to make some tweaks.

1) I used the 1/2" copper down to spout to avoid the shower rise / dribbling shower head problem with pex. But could/would using the 3/4" pex for supplies/shower head vs the 1/2" copper at spout actually cause restriction of sorts at the spout....and lead to the dribbling shower head issue?

2) Any pressure/flow issues with my setup that jump out? Would i be better off switching supplies to 1/2" pex, or converting tub spout to 3/4" ?
Installing a soaker tub, and hoping this setup wouldn't lead to painfully slow fill times. Weak shower head even less desirable.

seldomright said:

1) I used the 1/2" copper down to spout to avoid the shower rise / dribbling shower head problem with pex. But could/would using the 3/4" pex for supplies/shower head vs the 1/2" copper at spout actually cause restriction of sorts at the spout....and lead to the dribbling shower head issue?

Click to expand...

In theory, it could -- but in most cases the valve would be limiting the flow rather than the 3/4 inch pex, I would think.

How about using a valve that controls the flow to shower vs tub, rather than using a diverter spout?

The over sized tubing used to supply the shower valve will have Zero detrimental affect on your spout or shower head. The valve ports themselves are already necked down to 3/8". Your tub spout will work fine on 1/2" copper and your shower head likely operating at 1.75gpm will be more than adequately supplied through 1/2 as well.

Tuttles Revenge said:

The over sized tubing used to supply the shower valve will have Zero detrimental affect on your spout or shower head. The valve ports themselves are already necked down to 3/8". Your tub spout will work fine on 1/2" copper and your shower head likely operating at 1.75gpm will be more than adequately supplied through 1/2 as well.

Click to expand...

Yep shower head 1.75gpm. Thanks TR, makes sense.