Moen Posi-Temp Valve Uses No Backing Board?

[Bluegrass Picker]

I'm getting ready to install a Moen Posi-Temp shower faucet, and the instructions make no mention of any backing board or support other than the plastic round "plaster ground" sandwiching the fiberglass wall to the escutcheon plate. Apparently the valve "floats" and is held only by the escutcheon plate screws.

In the construction world is that the usual mounting method for these, and is that strong enough to withstand the future gyrations of cartridge removal, etc. since the escutcheon plate would have to be removed leaving the valve unsupported? Is it preferable to create a backing board to mount the valve onto?

My concern is if the plastic round "plaster ground" should ever break during maintenance, there's no way to wiggle a replacement in behind the fiberglass enclosure. We have hard water here, so a cartridge replacement once in a while might be a reality....

Thanks very much,

Bluegrass Picker

 

[Jadnashua]

It sounds like you're talking about the 'thin wall' installation. There is nothing to prevent you from using some pipe clamps or straps to anchor the supply pipes going into the valve to provide stability if there is no other provision to anchor the body of the valve in place to blocking. Some rough-in valve bodies have legs or screw holes, some do not. The reason they use the plaster guard on thin wall installations is to prevent the flexible wall from breaking the seal of the escutcheon and letting water get in behind. Even if you caulked that junction, it may not hold, but sandwiching the valve with the guard behind the wall, and the plate on the other side keeps that watertight, not to hold the whole pipe/valve from moving in or out. That's what the straps or clamps are used for, and would be the same for any install, tile, or thin wall.

 

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[Terry]

You can remove the clip with the plastic set to thin wall.

 

[Bluegrass Picker]

Terry and Jim,

Thank you very much for your helpful replies, and I appreciate this forum.

I think I'll install a horizontal backer 2x4 with a 1 1/4" hole drilled in the back for the unit to "float" in yet provide some stability. I'll be installing the shower "onto the valve" with the valve in place first, as opposed to installing the valve from behind after the shower is installed. There's no way for me to reach in back once the shower is set in, so the 2x4 will hopefully keep thinks kinda lined up until I can get the escutcheon plate screwed in. I'll clamp the pex and that along with the pex shower riser should help some also. I'm pretty picky on getting things done right the first time and I tend to err on the side of "heavy duty" and solid and properly aligned, etc....

Thanks again, and Merry Chirstmas.

Bluegrass Picker