Installing New Mixer Tap & Valves

[nooman]

Hi, I'm installing a new mixer tap in my kitchen. The current setup doesn't have any isolation valves so was thinking I'd cut the pipe, install a couple of flat faced isolation valves and then screw the flexi's into that. My question is, should I be using PTFE on the threads, joining compound on the olives or nothing at all? Seems to be a lot of conflicting advice online.

Thank you

 

[steadyon]

1. Never use PTFE on threads, except when the water seal is made on the threads themselves, which only happens on steel fittings, or on brass threaded fittings like bushes.
2. Compression fittings seal by compressing the olive between two sloping faces. This squashes the olive so that it forms a water tight seal with both the pipe and the fitting. On new fittings there is no real need for any additional sealant. On fittings that are being re-used it is prudent to wrap PTFE tape around the olive, or to use something like Jet Lube V2 or similar to accommodate minor marks or mis-alignments in previously used parts. Despite the foregoing, I use a little V2 even on new fittings, mainly to avoid any possibility of a call back.