Grohe Valve

[Marcus Mckenzie]

So i did a new rough-in for a tub/shower unit at a customers house ,(Grohe valve) i ran new 1/2 pex to valve at all four spots, when i went to test the water coming out of the valve ,water comes out of the spout & also the shower nipple too crazy i did look at valve and it was not installed upside-down ,also i pulled the cartridge and changed with a new one , help i don't know what to do.

 

[Hackney plumbing]

The pex is restricting the flow between the valve and the tub spout......this causes back pressure that relieves itself through the showerhead.

The "fix" is to replace the pex with copper from the valve to the spout.

Sorry!

 

[Sponsor]

 

[hj]

also, make sure it is not a valve that needs a "twin ell" for the spout to shower riser connection.

 

[Jadnashua]

Note, this 'problem' is not unique to any brand...pretty much all of them specify not to use pex to supply the tub spout and shower riser - sometimes, it's in the fine print, or in a picture with a cross through it, but it is generally there.

Many of the Grohe valves specify a twin ell. And, as noted, you CANNOT use pex, or at least the 1/2" stuff you have, to feed the shower riser and the tub spout. At the minimum, you'd have to run solid pipe to the tub spout; you might get away with pex to the shower riser. Neither of those would work if it requires a twin ell.

 

[Hackney plumbing]

You can use pex for the shower riser without issue except for decreased volume at the showerhead but thats not an issue typically.. You can substitute a twin ell fitting with a twin ell tub spout but choices will be limited on spout selection.