Hi
I am not a newbie to plumbing but I cant solve this one!
I wanted to change a radiator valve from 'manual' to a TRV. Simple enough. However, whatever I do, I cannot undo the fixing nut that attaches the existing valve to the radiator. I have of course also dented the copper pipe, but I can sort that out.
I have tried heating the nut, WD40, agression.
What else?
When redoing this setup, should I run PTFE tape in the joint or not?
David
I assume that you're turning it the right way? The nut pulls the flange on the radiator tail towards the valve so, to undo it, you have to turn it clockwise when looking towards the end of the radiator - i.e. *unscrew* it from the valve.
You will need a spanner with a long arm - a large adjustable is good for this. If the nut is tight, or caked up with Boss White - which it invariably is - applying a lot of torque will tend to rotate the whole valve - and bend the pipe, as you have already found. So this torque needs to be reacted - by such means as gripping the valve with a mole wrench (particularly if you are going to throw it way afterwards). In extreme cases, it may be a two-person job - one holding the valve and the other undoing the nut.
The tail to valve joint has conical faces, and is designed to seal without using any additional substance. I tend to put a very thin smear of Boss White on the mating faces - but don't overdo it!
I trust that you will be replacing the tail as well as the valve - not all tails fit all valves, anyway. You will probably need a large Allen key to remove the old tail - again requiring a decent amount of torque. It easiest to do with the rad lying flat on a workbench. Clean up the threads and use plenty of PTFE tape round the threads of the new tail.
The connector from radiator to valve is normally screwed in to the radiator with a captivated compression nut on the end that meets the valve. So, are you turning the compression nut in the correct direction? It may look like the valve connects to the radiator, but it's actually the radiator that connects to the valve.
Like the tail bit on the right of this picture:
You do need to support the pipework and valves when fixing them, and the best way is to have another spanner on the main body of the valve to hold it tightly while you undo the nuts. This stops the bending forces acting on other bits of the fittings that you don't want bending forces to act on while you do the job. Putting a hand on them to try and hold them isn't always enough, and a longer lever is usually needed to counteract the force of the spanner you use to work on the compression nuts.
I am turning it the correct way. I think it's holding the valve steady on the pipe thats causing the trouble as it seems keen to wobble around. However, I guess mole grips may help, and a mate to hang on to them.
Goodness knows what 'they' did with the valves, most in the house are like this.
Big Strong Boys these plumbers, eh? :-)
In message , David P writes
You can normally get another wrench around the body of the valve to provide some counter torque, a stilson is a good bet, if there's enough space between the valve and the wall.
As with most seized nuts, it can sometimes help to actually try and tighten it slightly. This can sometimes break the "stiction" and allow it to then be slackened.
Phil
A mixture of 'tightening' and long handles did it. And, despite what I said, not entirely sure I originally tried the correct direction to undo,
Thanks guys!
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