Radiator Valves and Compression Joints

ajbaker

Me again! I am in the middle of installing my own pipes/radiators for my central heating system, and need a little advice re the compression fittings on the radiator valves.

I have purchased Danfoss Randall TRVs but assume this will apply to any valve.

The valves have one vertical (to heating pipe work) compression fitting, one horizontal (to rad tails) compression fitting, and one horizonal screw thread that screws into the radiator.

Normally I am happy with compression fittings without using PFTE tape but feel I should use it in this application - most comrpession joints seal half a turn after making them hand-tight, however the joint to the radiator tail remains loose and still slides after this. Should I use PFTE here or just make it as tight as possible?

It makes sense to wrap it several times around the screw thread that is inserted into the radiator in order to seal that. However I am not sure it is best used on the two compression joints. It makes little sense to wrap it around the thread for the nut since it is not this that seals the joint. Should it be placed around the olive or would this cause more problems?

Thanks in advance for your advice.

f107btx

PTFE tape not needed on compression joints just a slight nip up to tighten.Too much tightening could distort olive

raymond

I always wrap a few turns of ptfe tape around the olive on any joint, but the reason you have problems with that particular fitting is that the tail you are tightening the olive onto is brass and does not compress like copper.

I was always taught to use boss white on all heating joints.

ajbaker

Thanks for the reply. I will try f107btx's suggestion with the radiator valves to see if they will seal without any PTFE, but I suspect raymond is right about the brass not compressing the same way as the copper. Even so, should it be possible to get the olive to seal on brass without the use of further products?

Please excuse my ignorance, but what exactly is boss white? Is it a paste that sets hard, or a silicon based gel? Will it be visible when used? Where exactly should it be applied - over olive, screw thread, on pipe etc?

plumb1_2

f107btx wrote:

PTFE tape not needed on compression joints just a slight nip up to tighten.Too much tightening could distort olive

Ptfe tape is not made for the purpose of wraping around olives, it is a thread seal tape. You should always used jointing paste, never just tighteen a compression fitting without it, why? my boiler keeps looseing prussure over a period of a few days, my carpet is damp and i cant see any leak, etc etc.
Boss-white is a hard setting paste, personaly i use La_co paste non-setting, it also has flakes of ptfe in it.

alanobrien

You dont really need to use anything with compression joints (mostly) but if you do want to use something to be sure it will not leak, then this stuff is excellent

Fernox Leak Sealer LS-X
http://www.plumbworld.co.uk/93-14509

weekendwarrior

alanobrien wrote:

You dont really need to use anything with compression joints (mostly) but if you do want to use something to be sure it will not leak, then this stuff is excellent

Fernox Leak Sealer LS-X
http://www.plumbworld.co.uk/93-14509

I'll second that, I never use anything at all with them and I have never had one leak yet!

quoia

Personally I'd use a smear of Boss white on almost any and every compression joint.
I've seen "dry" compression joints leak at finger tight plus quarter turn , and still at another quarter turn, and still at another quarter turn, and still at another quarter turn, and still at another quarter turn, etc.
I've undone one of these, added the tiniest smear of Boss white and it no longer leaks AT JUST FINGER TIGHT !!

Incidentally if you need some - B&Q - 98p for 400g - not found cheaper for non-potable use !

Mr_Proctalgia

I was thinking about this one! Can I ask if the olives are symetrical or not ( bet all the plumbers have just twigged on too)

ajbaker

Mr_Proctalgia wrote:

I was thinking about this one! Can I ask if the olives are symetrical or not ( bet all the plumbers have just twigged on too)

Not exactly sure what you mean by 'symetrical', but the olivers are of identical size (standard 15mm), and have an identical curve/indent/angle (whatever you wish to call it) on both sides. So yes, I would say they were!

I may well have some of the Fernox around so will give that a try; it sounds preferable to the boss white in that it does not set hard.

Many thanks to you all.

f107btx

weekendwarrior wrote:

I'll second that, I never use anything at all with them and I have never had one leak yet!

I second that too when compression fittings were first used PTFE tape was not invented so there fore could not be used likewise FERNOX Boss White and horse hair were only used by Plumbers older than me and i`m 70