Radiator - cold at the bottom but hot at the top

[swebb]

A radiator in one room in my house is as described... I have bled it and as expected, water came out straight away. The room is colder than the others - noticabley so.

I guessing the best way to solve this is to turn the other rads off, get this one hot and then turn the others on? Or is there something else?

Thanks.

[designermatt]

sounds to me that the rad may be silted up wiith rusty sludge atthe bottom and your system could do with a full rad flush and inhibitor process afterwards.

[swebb]

I should have mentioned... just over 12 months ago the whole system was completely drained and flushed out. The liquid (don't know what it's called) was put into the system and so it shouldn't be clogged up... should it?

[malamute]

You don't say how long the system has been running is it a bog standard system ?or where the radiator is located.
My first thought is to isolate it and remove it could be full of black sludge (take care prepare for spillage) take it outside and flush it out with a hose pipe keep doing it in both directions until the water runs clear.
Refit and bleed normal service restored?.

[Canucklehead]

Hi

Is there a valve at both ends or are the two pipes at one end with one valve?

Corgi Guy.

[swebb]

There are pipes at both ends. One end has a thermostat. It's an old rad, a double as well. Does that answer your question?!

I've just turned off two other downstairs rads. This rad has quite quickly gone very hot at the top, but remains quite cool at the bottom.

[Canucklehead]

Hi

I had a theory , but it's not right!

I would follow malamute's advice, and make sure the TRV is opening fully as well.

Corgi Guy.

[swebb]

Sorry - TRV?

[Canucklehead]

Originally Posted by swebb

Sorry - TRV?

Thermostatic radiator valve.

Corgi Guy.

[sexysam]

Hot at bottom and cold at top only means you have got some air in the radiator which is preventing the top bit getting hot.Use a key to slightly open the valves and let the air out ( hissing noise). When water starts to come out, close valve and the whole of the readitor should get hot

[MoJo]

I had a similar problem (hot top, cold bottom) that was solved by having the rads balanced - which sounded complicated but looked simple (make sense?) but apparently there's more than one way of doing it.
It involves making sure the temp outflow of each rad is lower than the temp of the inflow working round the system. Sorry I can't be more specific but I didn't pay that much attention at the time.

[red40]

Putting my plumbers head on here. I think my first question would be, was this particular radiator like this before the drain down and flush, you had 12 months ago?

[swebb]

Yes, the problem was there before the work was carried out. It did improve things a bit though (previously pretty much stone cold) after the work was carried out.

However, a couple nights ago I turned off the rads downstairs and waited. I turned the 'bad rad' onto full. This then became very hot (although cool/warm at the bottom). I then put the other rads back on, but not fully. Eventually, I got the other rads to their usual temperature and the 'bad rad' to a hot level. So in the end, one rad has a lower setting on the thermostat whilst all the others are on full.

The rad in question could be hotter but it is a lot better than it was. It's still only cool at the bottom.

[plumb1]

Originally Posted by swebb

I should have mentioned... just over 12 months ago the whole system was completely drained and flushed out. The liquid (don't know what it's called) was put into the system and so it shouldn't be clogged up... should it?

Was the system mearly drained and refilled, or did you flush all the rads out?

Imo take off the problem rad and flush it outside with a hosepipe to remove any sludge. Best of all have the system powerflushed.

[baby-mechanic]

Is there a wabsit that explains about draining and flushing central heating radiator systems ?

[Too Bloo]

This site might prove useful to you.




http://www.diydata.com/index.htm