Sealing Radiator Tails

[Colin Stamp]

Hi all,

A couple of weeks ago, I replaced all my radiator valves with TRVs and new lockshields. 5 of the 9 rads needed 3/4" to 1/2" bushes and four of those also needed tail extension peices on one end. I make that 32 joints, not including the ones with olives. I used PTFE tape on all of them.

It all went swimmingly except for three joints, which weeped very slowly. I tightened them up - only one stopped weeping. I re-assembled the weeping ones with loads of PTFE tape - still weeping. I re-assembled them with PTFE tape and LS-X - still weeping. I bought new bushes, in-case I'd cracked the old ones, and re-assebled one with PTFE tape - STILL weeping. I'm getting a bit peeved with this...

Interestingly, all three of the weeps came from between lockshield tails and bushes. There's only 6 joints with that combination on the whole system. Surely that can't be a coincidence?

The lockshield valves are all PTS own-brand. I think I'll try getting some of a different brand and use the tails off those. Does anyone have any sure-fire ways of getting the bloody things to seal?

Cheers,

Colin.

[A.Lee]

More tape, more decent sealant - not LSX, use a 'boss white' style sealant, and do it up really tight.

[Andrew Gabriel]

I usually start with 10 turns of PTFE on radiator tails. If the tail hasn't got stiff to turn before it bottoms out, disassemble, strip and discard the PTFE, and repeat with 15 turns. I don't think I've ever needed more than that.

Also, make sure you put the PTFE on the right way around, so that screwing it into the radiator is effectively pulling it tighter, not undoing it.

[Roger Mills]

Use gas-grade PTFE tape - it's much tougher than the usual stuff.

[Colin Stamp]

Thanks to all who replied. I went out and got a pair of new valves at lunchtime, came home this-evening to fit them only to find the pump had packed up. Now I've fixed that, I'm all plumbed out for tonight. The tails will have to wait until tomorrow.

The pump was particularly annoying since I knew it was on the way out and I have a Grundfos Alpha 2 on back-order. Now I've ended up fitting the cheapest one Toolstation sell and I can't decide whether to cancel the Grundfos order or not...

Cheers,

Colin.

[Colin Stamp]

Well, both the new tails sealed nicely with and 10 turns of PTFE (which is less than I tried on the original tails at one point) and no sealant. I guess it was something strange about those particular PTS tails and the brass bushes. Weird!

Cheers,

Colin.

[fred]

In article , Colin Stamp writes

Your experience was similar to mine a few years back (a few weeping joints out of 12 or so rads) so I switched to one of the liquid ptfe type sealants and I haven't used ptfe tape since for water work, liquid has sealed all joints first time since.

Others here have reported ptfe tape being ripped by burrs on internal rad threads and have had some success by cleaning up those threads with a tap but life is too short and I'll stick to liquid sealants.

[Andy Wade]

Yes, where the threads are a bit rough and the fit is loose I tend to use good old fashioned paste (boss white, etc.) and hemp. I've never has a joint leak, done that way.

[PeterC]

Same here - had a brand-new Stelrad and couldn't seal a thread with any amount of any sort of tape; bit of Hawk White and job done. I often use it in small amounts even if not needed as it 'lubricates' the whole joint so that all of the 'feel' is in tightening rather than friction.

[Colin Stamp]

Yep. My faith in PTFE tape has taken a bit of a battering during this last job. I've never liked these threaded joints. I reckon they can sense the presence of dodgy DIY plumbers.

Cheers,

Colin.