Wall plate elbow for Grohe isolating valve with ribbed thread

[jacoscar]

I have bought a nice pair of Grohe angled isolation valves for my basin (floating with no cabinet underneath, so the valves will be visible). However these have a ribbed thread that needs to seal against a rubber washer. I have bought some Flomasta wall plate elbows 15mm x 1/2” to go behind the plasterboard and tiles, but they are supposed to be ‘thread sealed’ with PTFE and don’t have a washer. What do I need instead?

I know the easy way would be to just return the Grohe valves and buy these https://www.toolstation.com/flat-faced-male-angled-isolating-valve/p31424

 

[Madrab]

Fitting tap isolators with pre-roughened threads

Hi all, I bought these tap isolators: https://www.grohe.co.uk/en_gb/angle-valve-1-2-22037000.html So how do I fit the pre- roughened ends? I assume they go into wall plate elbows fitting inside my stud wall. Do you put PTFE tape on them (and how many windings should you use)? Cheers

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