Should I use PTFE tape on threaded olive connections? I can get then water tight but I have to tighten them up so much I worry I will break the thread (though I haven't yet)
Also I assume you use plenty on threaded connections e.g. a TVR valve into a radiator?
PTFE should not be used anywhere near the sealing surfaces. One layer on the sliding surfaces makes a good lubricant to ease tightening them up -- that's the thread, and the back of the olive, but not the front or inside of the olive.
If a compression fitting has failed and won't stop leaking with appropiate tighening, the PTFE on the sealing surfaces can sometimes make a reasonable bodge-it repair.
Yes. Radiators and tails vary, but I tended to start with 10 turns. If it screwed all the way home without getting tight, dismantle, discard the used tape, and repeat with 12-15 turns.
I never put add anything anywhere near any compression fittings - just make sure everything is clean, bright and undamaged - that is how they are designed to be used
Indeed - I always do this even if it does tighten - fill the threads with PTFE by screwing in, then remove, add more and make the final seal.
It sounds like you might be overtighening them, resulting in a worse seal (possibly through deformation).
My rule of thumb is to hand-tighten the nut then add half a turn with the wrench (marking the nut/body can help if for some reason you need to do this in two go's e.g. limited access).
Mathew
No, compression joints should not require any thing other than finger tight plus 1/2 to 3/4 of a turn. A smallest smear of something on the inside of the nut to act as a lubricant is sometimes helpful.
Presumably 'cause you've got lots of PTFE stopping the olive bite the pipe properly and seal against the fitting.
Cast iron and other parallel threaded stuff is about the only place to use PTFE tape.
In spite of what I said, I agree with you. I've only used it on large compression fittings where the librication was helpful. Never do this with gas pipework though, as you wouldn't be able to prove you hadn't got some PTFE into one of the seals.
Is the TVR the sports version of the TRV ? :-)
It's the one that bits drop off on a regular basis until it seizes up and stops working. I think all of mine were like that when I bought the house because none of them lasted long.
PTFE tape is designed for use on tapered threaded connections - where the seal has to be made within the threads. [When Adam were a lad, Boss White and hemp did the same job - albeit a bit less tidily]. So you should certainly use tape when screwing radiator valve tails into radiators.
You should *not* use it on compression joints which - if done properly - seal perfectly when assembled dry. If you *must* put something on them, a smear of Boss White round the olive is preferable to PTFE tape, but probably acts more as a lubricant while doing it up than as a sealant.
You should also not use tape on parallel threaded joints - which are designed to seal by means of a rubber of fibre washer between two mating faces, rather than on the threads per se.
I found that very interesting cos I have been using PTFE on compression. I will try to do without now. So where does "Boss White" fit into this then ?
Richard
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I think Boss White was just one particular make. It's the same stuff as
I still use it on 'difficult' compression joints - especially if I have to dismantle and subsequently re-assemble a joint.
Whilst on the subject of sealing pipe threads, I gather that PTFE *liquid* such as
Maybe it will replace PTFE tape *and* Boss White?
Bob made the most significant point - cleanliness! A bit of grit can ruin a good seal.
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I used it (actually Screwfix 'No Nonsense' brand) for the tails of the three new radiators to TRV's and lockshields that I installed here recently and it worked a treat.
It will for me ;-)
With careful application, just a smear all over the threads, it lubricated the threads well and helped with the doing up and left me with only a slight ring of the stuff that was easily wiped away. Far better than trying to pick away bits of PTFE tape that would have protruded and spoilt the appearance of the chrome TRV4's!
But, as this has been said before in this thread (sorry for pun), it or any other sealant is not intended to make olives watertight.
Steve
On joints that make their seal using threads. However string (aka loctite
55) and resin (e.g. Liquid PTFE) do the job better, IME.
I use PTFE on the threads of compression joints - only 1 or 2 turns - simply as a lubricant. Agreed never on the olive.
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