Leaking radiator

tigerlily59 · Jan 3, 2017

Hi

I wonder if someone can help, the pressure in my boiler keeps dropping and I am having to keep adding water to it to bring it up to 1.5, I have discovered that I have a leak on one of my radiators so this seems like a good explanation. I have done loads of reading this morning but most of the leaks that I have read about are at the bottom of the radiator, but the leak I have is from the nut on the top left, opposite to the side where I would bleed it, it also only leaks when the radiator is cold.

I am guessing, from what I have read that I would turn both the bottom nuts clockwise to isolate the radiator, then loosen the top nut add some PTFE and do the nut back up. Does this sound correct, or is there a different procedure with it leaking from the top? Should this be done when the system is cold?

Also, anyone know why it only leaks when cold?

Many thanks for your help

Michelle

steadyon · Jan 3, 2017

1. Turn valves at left hand and right hand sides of radiator to off position.
2. One should be a lock shield valve for which you will need to take the cover off then use a spanner or (if nothing else available) pliers to turn valve clockwise (looking down on it). Count the number of 1/4 turns to fully closed so that you can open it the same number of 1/4 turns later to preserve the balancing of the system.
3. The other may be a thermostatic valve (TRV - numbers on a ring round the outside) or what is called a wheel head valve. Turn fully closed (clockwise from above). Make a note of the number of 1/4 turns, although not so important as for the lock shield valve.
4. Bleed the radiator as normal. Expect virtually nothing to come out. If more than a dribble comes out, and persists for more than a few seconds, then one or both of the valves is not shutting properly. Probably time to call for assistance.
5. Assuming valves have shut, check blanking plug at opposite end from bleed point is tight. They mostly seal with a black rubber "O" ring. If slightly loose, tighten and carry on as at 6. below. If not loose, remove, wrap with PTFE tape (8 to 10 wraps), wound on in the same direction (clockwise looking at the outside of the plug), replace and tighten plug.
6. Close bleed point, open valves the number of turns originally closed, and check for leaks.

I can't tell you for sure why it only leaks when cold. The only explanation I can think of is that the plugs are usually made from chrome plated brass, while the radiators are generally steel. Brass expands more than steel when heated, so the differential expansion my be just enough to take up any slight gap.

tigerlily59 · Jan 3, 2017

Thank you so much for that, you have give me a really clear explanation and it is much appreciated. I'll get some of the PTFE tape and have a go.

Michelle

JCplumb · Jan 3, 2017

The blanking plug is usually fitted with a rubber seal, have you tried just nipping it up?

tigerlily59 · Jan 3, 2017

I've tried to tighten the nut as much as possible but it still leaks. Is that what you mean by nipping it up? Sorry I'm no good with the technical terms :smile5:

joni os · Jan 3, 2017

It probably leaks slightly when hot, but is unnoticed due to evaporation. If you have PTFE tape available wrap at lest 5 thickness in a direction, so when screwed in,tape is smoothed into threads rather than become unravelled. If you have to buy, go to plumbers merchant and purchase locktite 55. for a more positive result. Usually a single wrap around all the threads will suffice.
If your boiler is pressured you may have to bleed off a lot of water to reduce pressure but once reduced, and water ceases to exit vent, close vent and other end can be removed even it valves do not completely shut off.( You will have created a vacuum.)

JCplumb · Jan 3, 2017

tigerlily59 said:
I've tried to tighten the nut as much as possible but it still leaks. Is that what you mean by nipping it up? Sorry I'm no good with the technical terms :smile5:

Yeah sorry, I meant tighten it.
As already said you just need to close the valves and bleed the rad until the water stops coming out.
Then undo the blanking plug, some more water will come out, a towel should easily be enough to soak it up as it comes out, then a good few wraps of ptfe or loctite 55, or just get a new blanking plug from a merchants, shouldn't be more than a couple of quid and will come with a shiny new rubber seal on it.

*Edit* I just googled new blanking plug and they're £1.39 at Wickes and come with a bleed plug and bleed key too.