Central Heating Question

One radiator cold despite system drained and mag filter fitted and flushed

I have replaced all 12 radiators in my bungalow as the old school type cast iron radiators were just not hot enough.
I have had double radiators fitted.
I had the system drained and a mag filter fitted and flushed. Apart from one radiator the rest are hot. I have bled it several times, I shut off one end valve and bled it and good pressure, I closed the other end valve and bled it but it seemed a weaker pressure, yet this is the end that the heat gets to. It just won't enter the radiator and pass through it.
I have shut off all the other radiators and operated the heating system to try and force the water through but still cold.
Could the pipes still be blocked up with sludge or what could be the problem?

2 Answers

have you pressure cleaned your system ,each circuit is power flushed so if any thing is in that supply it will be cleared under pressure

Answered 27th Oct 2013

George Giles Home Improvements

Member since 2 Nov 2008

It sounds like you have either a stubborn air lock or a pipe blocked with sludge or debris.

Depending on how handy you are, you may be able to bleed an air lock out yourself. Simply opening the rad's bleed valve won't be sufficient.

Turn off your system and allow it to cool. Getting wet is one thing, but you don't want to get scalded.

Close off both radiator valves tightly. Bleed the rad as normal until water stops coming out. Then remove the bleed valve completely, not the small part you put your key on, but the whole 1/2" bush. Now connect a hose to the opening, I use a 1/2" male iron to 15mm push fit connector with a short section of pipe in there, connected to a hose via a lever valve. Once this is connected, close off the lever valve and open one of the rad valves fully. Opening the lever valve now will allow any air in the pipework to be released. If you have a combi boiler, you will have to top the pressure up as you do this, and you may aswell leave the filling loop on half way.
Close the lever valve, close the rad valve and open the other rad valve. Opening the lever valve should remove air from the other pipe.
Close the rad valve, so that both are now shut, and remove the hose etc. Re-install the bleed bush, using PTFE tape if necessary, although your rads are new so they'll probably include rubber O-rings instead.
Turn off your filling loop and check the pressure. If its too high, simply bleed a radiator to release some pressure. If it's too low, top it up in the usual way.
Now make sure both valves on the faulty rad are open and turn on your system. in 99% of cases, this will have your rad hot again, if it doesn't then the problem is either sludge or debris in the pipework which will mean you'll have to call your powerflush man (or woman!) back.

Answered 1st Feb 2015


Member since 7 Nov 2014

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