Hi guys,

We seem to have an issue where some of our radiators do not work.

The boiler was serviced this year, the system has pressure and the radiators are all bled. However two of our radiators just don’t switch on.

Most of ours have the same thermostatic valves as the problematic pair, could it be as simple as just that the valves on these two are bust?

I’ve changed radiators and valves many times – so it’s a simple but potentially messy job, so I’m looking for some ideas first.

Shut off all the other rads and run the heating – this will hopefully move any air lock that may have developed – see if they then heat up.
We have one rad that refuses to work after the system has been drained despite bleeding successfully. The above routine fixes it.

Most of ours have the same thermostatic valves as the problematic pair, could it be as simple as just that the valves on these two are bust?

Yes it can.

But the first thing to do is undo the little retaining ring on the thermostatic valves, remove the plasticy top bit and check that the little metal pin thingy attached to the radiator pipes can move up and down without too much resistance.

Here you go

Dont know what type you have but if there is some heat at the bottom, and cold at the top, its a sign they’re full of air and need bled.

Perhaps a balancing issue – close all the valves on the other radiators, and open (set high) the valves on the suspect ones, this will force your pump to put all its efforts into your suspect ones. The results of that test determine what you do next..

IANAP.

I’ve just done the same thing on mine, bought two cold ones back to life.

We think we’ve just fixed this. Is it a combi boiler? Have you got a hot water tank? Turns out that our combi boiler can’t both do hot water and heating at the same time – our hot water was really hot and the upstairs rads were good, but downstairs rads were mostly cold.

We reset the hot water to just do mornings and evenings and the rads are all toast warm now.

Cheap TRVs? Sometimes ours won’t fully open even on max I end up just taking heads off, you just undo lock ring quick to check.

Go with sharkbait’s option first. Turn off all rads, leaving one of the problem rads on, one off. Turn heating on, this will push air lock off. Then open next problem rad. If either of these don’t heat up then you’ve got a TRV issue.

As with Sharkbait, we have one radiator that won’t come on if the system is bled. Turning all off, then turning back on cures it and moves the air to one bedroom radiator, which I just bleed there.

Turns out that our combi boiler can’t both do hot water and heating at the same time

AFAIK non can, they have a diverter valve that switches the flow over to the secondary heat exchanger when there is HW demand.

Turns out that our combi boiler can’t both do hot water and heating at the same time

AFAIK non can, they have a diverter valve that switches the flow over to the secondary heat exchanger when there is HW demand.

So it seems! So the first thing, before anything else, is check that your hot water isn’t permanently on.

Lots of heating and plumbing threads recently! I have to start messing with mine when I get home from work.

We have this problem, and also some others. I’ll try and free off the valve before I start removing radiators to flush them out so thanks for the youtube clip.

Check that the pipe coming out the floor is hot. If it is then it’s definitely a valve issue. I had this recently in the attic, never thought to check how hot the pipes were. Plumber came round and fixed them all in 30 minutes.

Remove TRV from one each of working and non-working rads; swap them around and turn heating on.
If non working rad now works and vice versa, just replace the non-functioning TRV.
While the TRVs are off, check up and down movement of spigot/pin; a spray of WD40/GT85 may help.
If this doesn’t work, find a local plumber

I’ll try and free off the valve before I start removing radiators to flush them out so thanks for the youtube clip.

If you suspect a blocked rad (warm at the top but not the bottom) you can use the same trick to help clear it – switch off all the other rads to force the flow through the blocked rad.
Tapping with a rubber hammer can help dislodge crap.
That hopefully gets it moving but then you need to get it out of the system – which is where something like a magnaclean comes into play.

Screwfix sell just the heads, so undo the shiney lock ring. Remove trv head. That rad inlet should now be fully open, so switch all other trvs to frost or *.
Turn on ch
Let us know the outcome.
Buy new trv head if rad works.
If new trv doesn’t help then its a balance issue and you need to back off the flow to the others via the locksheild valve.

bookmarking for this weekends plumbing based fun

If none of the above works it can also be debris restricting flow inside the heat exchanger on the CH side.

It’s usually the rads on the end of the circuit that are most problematic. Modern microbore piping is more prone to blockages!

I just fixed my top floor, en suite radiator which has never worked using that method in the video! Can’t wait to step out of the shower in the morning and hopefully not freeze stiff like normal.

Everyone – many thanks. I’m at home tomorrow and will try the advice in the order suggested. I’ll report back and let you know! Thanks again!

also bookmarking due to the good advice on here…..