Replacing old radiator tails

[ozgirl]

Hi,(first post-slightly nervous...)


I have old imperial size radiators and need to replace the valves (all 5 are different, most leak, and 1 is rusted to the point of disintegration). The rads themselves look fine, and if possible I'd prefer not to modify the pipework.


I've taken out the old rad tails (the type that need a 1/2 inch hex key), and tried to replace them with the rad tails that came with the new trvs (the kind that need an adjustable wrench) but the new tails only seem to screw in about 8mm ie about two thirds the length of the screw thread. The result is the whole thing is now too long to fit the old pipework (by about 7mm, more than 'persuasion' can manage on old pipes).


Am I not tightening them enough (even without ptfe they don't seem to go in any further, though I can't see any obstruction, different thread maybe)?
should I go buy some new rad tails which are the hex key rather than adjustable wrench kind?
or have I just missed something fundamental?


Probably should have mentioned that I've replaced rads before (like for like) but this is my first time trying to replace valves, so many thanks in advance for any insight/advice.

 

[Billy Bob Bob]

sounds like you have 3/4 nuts by 1/2 thread tails changing them to 1/2 nuts by 1/2 inch tails does sometimes make them hard to fit if theres no movement in the pipework i suggest you buy some 3/4 nuts by 1/2 thread tails in 15mm valves if you have 15mm pipework should make life easier

 

[Whyme]

rad tappins are all the same size even if there very old. Also same thread forever and a day. Their not cross threading are they ? Rad valves are parallel thread usually so they should go all the way in..V strange.

 

[Ch4 plumbing]

Take them out and clean the female thread, make sure you get all of the old carp out, old ptfe or hemp and dried paste!!
then wind the new tails in without ptfe to see how your doing, when your happy make in properly.

 

[Neil K]

Make the new rad tails in dry first ie. No ptfe or hemp or loctite on them. Wind them in as far as they can go and out again. This cleans out the female tread in the old rads. Do this and cut out the rad paint around the rim aswell, this will help you get them tailpieces in more once you make them in for good.

 

[Dotty]

Treat yourself to one of these.

1/2 x 14 BSP taps

 

[ozgirl]

Thanks all
I've given the threads a good clean, and run the tip of a very thin knitting needle round from top to bottom of the whole screw thread to make sure there aren't any obstructions - unfortunately that didn't make much difference.
You're right gas man, when I had a good look, the old rad tails are 3/4 and the new are 1/2. It also looks like the old ones are 'standard' and the new ones are 'telescopic' (hopefully using the right terminology here).
Went down to the local plumbing supply to try to get some shorter tails, but got a 'save yourself the hassle and just hire a plumber love', so I'll try a different store tomorrow.
Alternatively, would it be feasible to hack (say) 7mm off the end of one of the telescopic tails with a junior hacksaw/pipe slice? They look like chrome, so I'm guessing they might be a bit of a chore to chomp through?
Once again, many thanks for your all help.

 

[Ch4 plumbing]

I've used a junior hacksaw to shorten the tail when it's been really tight, new blade will go through easily.

Just don't cut them too short or the olive won't have enough to bite onto......

 

[ozgirl]

I've used a junior hacksaw to shorten the tail when it's been really tight, new blade will go through easily.

Just don't cut them too short or the olive won't have enough to bite onto......

Thanks Ch4, I've done just that and used a junior hacksaw to take a few mm of the end of one of the tails, and all fits nicely now. Thank you for the advice, problem now solved