Gravity feed radiator not heating

[Yeldua]

The radiator in our bathroom is gravity fed. It used to run as hot as the hot water. Although the pipe feeding directly into the radiator is still at water temperature, the radiator now is only barely warm. The radiator has been bled. The hot water tank is in a cupboard adjacent to the bathroom.

Advice would be most appreciated.

WTA

Yeldua

 

[ChrisR]

Sticking trv? Sludge? You could try flushing the rad in the garden with a hose - plenty on the forum about that. When rad is off connect a hose to the valves and open - should get a good flow from both sides with heating off.

 

[Yeldua]

Hi Chris

Thanx 4 ur suggestion. We've already replaced the radiator and piping ... brand new both hasn't resolved the problem.

Yeldua

 

[ChrisR]

TRV? Did you change the pipe run or move junctions?

 

[Yeldua]

Nothing moved. Just replaced exactly as was.

 

[breezer]

so if the feed pipe is hot (rad warm) and its a new rad, would that not mean one of the valves is at fault?

have you tried turning both valves off then on?

if trv (thermostatic radiator valve) it may be stuck. search the forums for trv

also what happens if you take rad off and open (slightly) both valves, any water?

 

[Yeldua]

Hi Breezer

Thanx for your ideas.

We have tried turning the valves off and on but didn't resolve the problem.

We'll try your suggestion of taking the radiator off in the morning and in the meantime I'll try a trv search.

Cheers

Yeldua

 

[ChrisR]

Why did you change the rad? And the pipes? Couls be a blockage in the pipe near where the feed pipe joins the system, which could be nearby. Is the rest of the system fully pumped?

 

[Yeldua]

Hi Chris

We changed the radiator and the pipes because they were old and as all other attempts to resolve the problem failed.

The hot water is reaching the radiator as the pipe where it joins it is hot. It's just not getting in there at full temperature.

The rest of the system is fine.

 

[Yeldua]

I've just been doing the TRV search that Breezer recommended and reading through realised I perhaps should have mentioned a couple of other things ... ... afraid my knowledge of plumbing only = water comes out of the tap!

The bathroom radiator is not part of the main heating. It runs direct from the hot water tank so is always hot (used to be always hot!) whenever the boiler is on ... which is all the time.

The old radiator didn't have a trv. The new one was supplied with one, but when the radiator wasn't warming up we took it off and that hasn't made any difference.

 

[ChrisR]

It would have a better chance if the input to the rad was on the top corner - suppose you don't have the right sort of rad?

 

[Yeldua]

The old radiator before it gave up worked fine with the input in the same place at the bottom

 

[ChrisR]

Yes you told us. But something isn't as it was and none of us is psychic! The driving force for gravity circulation in a rad is tiny - it takes very litle to stop it. You could try a £500 powerflush...

 

[krispy]

Hi Yeldua
If you are correct and the rad/towel warmer does indeed run from the hws tank there may be a secondary hot water pump on your system that needs attention. If not then as it may be fed from secondary water scale may be your problem. you must check both flow and return feeds. shut both valves and remove vent pin, open the flow and check the pipework runs hot, then shut the flow and check the return in the same way. A bin bag works well to catch the drips!!!

 

[ChrisR]

Surely it isn't on the tap water side?? That would mean you would have to have a copper radiator or towel rail, otherwise it would corrode at a prodigous rate