Fixing tiny weep on radiator thread

13 Apr 2012
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United Kingdom
I have a very small weep coming from where the radiator valve screws into the radiator itself and would like to have a go at fixing this myself. Is it possible to fix this whilst leaving the radiator in place on the wall? I was thinking of the following – isolate the radiator, undo the compression nut on the rad valve, drain the radiator, then unscrew the tail from the radiator. Remove existing PTFE and fit more, then reassemble. Would this be the correct way to do it, or does the radiator need to come off the wall?
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Fine to leave the rad where it is, just isolate both sides of the rad (careful if one valve is a TRV).
Consider your inhibitor levels before refilling?
John :)
Depending on the size of the rad, and the pipework 'moveability' what you suggest is possible.
Get a 1/2"bsp plug, even one of the plastic ones used to plug the rad holes for shipping will do.
Shut both rad valves and bleed the rad to reduce the pressure in the rad to zero....if the water doesn't stop coming out then the rad valves aren't holding.
Remove the valve at the leaky end, and put your finger/thumb/toe over the open end while you undo the leaking spigot....plug the end, the water should not glug out with the plug even loosely in place.
Re wrap the spigot thread, remove the plug (and any old PTFE tape) using a towel to catch any leakage.
Reassembly, as they say, is the reverse of the disassembly.
MeldrewsMate, do you think it'll be possible to avoid draining the radiator? Removing any old PTFE in the female threads of the rad would be near impossible whilst the rad is full wouldnt it?
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As MM's mate says, it's perfectly feasible to plug the rad tail orifice - the theory being that if air / water can't get in, then the existing water can't escape.
It could be a good move to remove the rad for a flush, if the water inside is black (add inhibitor afterwards).
Personally I'd use a quality sealant on the clean threads first, followed by ptfe and then another smear of sealant - and screw the tail in tight.
John :)
Not sure I'm totally following this! With the bleed nipple closed, and the valve union unscrewed (with my finger over the end of it), when I then unscrew the spigot, water will flow out pretty sharpish from the rad until i plug it. The when it comes round to refitting the spigot, it's not going to be easy screwing against the tide, so to speak!
Stop all the faffing about and drain the rad. If you're worried about inhibitor levels then remove a top plug and funnel a bit in before refilling.
OK, I agree I’ll be draining the whole radiator as it will be easier that way. It’s a sealed system, so once it comes to refilling the radiator, what’s the best way to do it? The radiator is downstairs, so once I open the valves at both ends will I need to open the bleed nipple to allow water back in? Is it then a case of filling up via the filling loop then going upstairs and opening the bleed valves on the highest rads, that’s where the water will have moved from to fill the downstairs rad? Or do I need an accomplice on the filling loop with me going round each radiator and bleeding?
It may save you a bit of a problem if you close off the other rads, then make sure the boiler is up to pressure, open one rad valve with the bleed nipple open. Close off, repressurise again and continue until the rad is full.
Open the other rad valve of course.
Check pressure, open the other rads, switch boiler back on and bleed......the chances are, the other rads will be fine. Ensure they all get uniformly hot.
Check pressure again.
A helper standing by the filling loop is a boon here, but don't over pressurise as you don't want the pressure relief valve on the boiler lifting.
John :)
It may save you a bit of a problem if you close off the other rads

I'm aiming for minumum disruption possible so was hoping not to have to touch any other rads. What bit of a problem could I expect if I don't bother?
Probably very little, as it happens......just get the boiler pressure up, open the bleed valve, and then introduce water slowly from both valves, listening for the escaping air. Close off before the pressure completely drops, pressurise again and repeat until all air is evacuated from the rad.
John :)

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