Roughing in Shower Valve w/ no Mounting

[JeffeVerde]

I've got a mixer and several volume controls to rough-in (multi-head shower), and was surprised to see that there are no mounting bosses on the valve bodies. I can't simply hang the valves off the piping, as my supply is PEX and I had the wall framed with an extra wide bay to accommodate valve and sprayer placement.

What's the best way to mount a boss-less valve w/ PEX -- copper stubs and then strap the stubs to blocking? Anyone got a slicker method?

 

[Terry]

You need something solid to strap too, so If you can't strap the valves, you will need to add some copper piping to them that can be strapped.

You mention that it's a shower valve, but for those that are installing a tub/shower valve, remember that PEX can not be used for the tub spout. It will force water up and out of the upper shower head when filling the tub.

 

[Sponsor]

 

[hj]

You use 1/2" or 3/4" brass nipples and fittings to connect everything together, then mount the assembly in the wall.

 

[JeffeVerde]

You mention that it's a shower valve, but for those that are installing a tub/shower valve, remember that PEX can not be used for the tub spout. It will force water up and out of the upper shower head when filling the tub.

Yep - that's what I was picturing.

Curious about the PEX-spout thing. What is it about the PEX that it restricts the spout flow enough to cause a backup out the shower head? Or is the real issue "don't use *undersized* PEX between the mixer and diverter"?

 

[Jadnashua]

Most diverters don't 'switch' the flow from one pipe to the other (although some do)...they rely on gravity to preferentially cause water to flow out the tub spout, and if you shut that off, it then forces it out the shower. But, if the water can come in quicker than it can go out to the spout, it backs up and will eventually cause some to dribble out the shower arm. Think about it...you rarely are using all hot or cold, so you have two pipes coming in, and then the internal restrictions of the valve with one pipe diameter out. If the path to the spout is restricted (pex OD is the same as copper, but the ID is significantly smaller), it will give problems. You can have problems with CPVC as well since its wall thickness is smaller than copper, too.

Plus, since you usually want to fill the tub as fast as you can, you want the largest opening the valve supports.

The instruction sheet for most (all?) tub/shower valves warn to not use pex or cpvc between the valve and the tub spout. Also, you want the tub spout to be well supported, and that's harder with pex.