To ptfe of not to ptfe

[DirtyNinja99]

Hi im hoping someone on here can offer some sound advice. Ive bought new taps and flexi hoses for my bathroom sink. They are plumbed in using solid pipework. Underneath the sink halfway down the pipe is an isolation valve for both taps, there the kind where u have to use a flathead screwdriver to turn. When i turn them a bit of water squirts out when its halfway through the turn then stops when its fully turned one way or the other. Is this normal? Im thinking i need to attach a small piece of deburred new pipe to the isolation valve then flexi hose to the new pipe then obviously the flex hose to the tap tails. Im aware of how to do most of it but need to ask should i wrap ptfe tape or put sealing compound like plumbers mait on and under the new olive also how many turns after hand tight should i go as i dont want to over tighten. Also will it be hard to get the old olive and pipe out of the isolation valve and if sealing compound has been used previously will i be able to remove it. Thanks hope someone with experiance can help as i heard so many different opinions on other forum which is making me unsure of how to do it.

 

[steadyon]

1. New olives in new fittings = no PTFE required. I tend to use a small amount of JetLube V2 wiped onto the compression edge of the fitting and round the inside sealing face of the compression nut. In theory not needed, in practice saves going back if there is a small weep.
2. The isolation valves you have are probably not full bore valves, but have a hole through the ball in the centre of around 10 mm diameter. this is restrictive of flow. Not important if your supplies are mains pressure (combi or unvented hot water), but will reduce flow if the supplies are tank fed. If you have the opportunity, change them for full bore valves. You can get them with butterfly handles, which are easier to use than the screwdriver slot. Get decent ones such as Pegler if you want them to last.
3. If the flexi hoses end in 15 mm compression fittings, your idea of a short piece of pipe is correct.
4. However, many end in 1/2" or 3/8" BSP threaded female fittings. These shouldn't be connected directly to the isolation valves, which unless a special type are not flat faced to seal to the flexi's, and the 3/8" one won't fit anyway. Use adaptors such as Screwfix 2665R (1/2") or 6089R (3/8") to connect.
5. Compression nuts tightening - comes with experience, but if you start at very firm finger tight plus 1/2 a turn you won't go far wrong.

 

[DirtyNinja99]

1. New olives in new fittings = no PTFE required. I tend to use a small amount of JetLube V2 wiped onto the compression edge of the fitting and round the inside sealing face of the compression nut. In theory not needed, in practice saves going back if there is a small weep.
2. The isolation valves you have are probably not full bore valves, but have a hole through the ball in the centre of around 10 mm diameter. this is restrictive of flow. Not important if your supplies are mains pressure (combi or unvented hot water), but will reduce flow if the supplies are tank fed. If you have the opportunity, change them for full bore valves. You can get them with butterfly handles, which are easier to use than the screwdriver slot. Get decent ones such as Pegler if you want them to last.
3. If the flexi hoses end in 15 mm compression fittings, your idea of a short piece of pipe is correct.
4. However, many end in 1/2" or 3/8" BSP threaded female fittings. These shouldn't be connected directly to the isolation valves, which unless a special type are not flat faced to seal to the flexi's, and the 3/8" one won't fit anyway. Use adaptors such as Screwfix 2665R (1/2") or 6089R (3/8") to connect.
5. Compression nuts tightening - comes with experience, but if you start at very firm finger tight plus 1/2 a turn you won't go far wrong.

Brilliant youve answered everything ive asked there. The flexi hoses do end with 15mm compression fittings. Very much appreciated. Cheers pal

 

[John.g]

Re new olives/new fittings, before I tighten the nut I ensure the pipe end is hard up in the fitting and then pull it back a few mm before tightening the nut, I reckon the pipe end has room to move in due to the olive compressing a little and don't use PTFE then or on the very rare occasions that I reuse the fittings.