Blocked Valve, Cold Rad - is flushing the answer?

[KeenAmateurUK]

I have 2 cold radiators (tall towel rails to be exact) which stubbornly refuse to heat up. I have an oil boiler and an F+E tank in the loft. The towel rails do not have TRVs, but have a lock-shield on each pipe instead.

I started by bleeding all the radiators in the house with no effect. I've tried closing off all the other radiators in the house, but I only achieved a whining central heating pump. I then took one of the cold radiators off and blasted it with a hosepipe to remove a small bit of sludge build-up, and it was at this point I realised that there is no flow through one of the lock-shield valves. I can open the bleed and the left-hand valve and warm water will eventually flow through into the radiator, but if I open the right-hand valve only the faintest few drops come out. I then tried attaching a hand-pump to the right-hand valve (thanks to a tip on here somewhere!) but after putting quite a bit of pressure in I wasn't able to clear any blockage. The pipes run under the tiled floor so I can't follow them to see which is the flow/return.

1. Do you think it is a blockage in the pipe or might it be an airlock?
2. Would draining the system and adding X400 (or similar) help, given that there is no flow going into/out of the radiator? Could I add it directly into the cold rad instead?
3. Is it worth paying out for a powerflush or is there anything else I could try first?

Thanks in advance!

 

[kidgreen61]

Sounds like you have a blocked pipe, I feel your pain.
Can it be re-piped easily?

 

[KeenAmateurUK]

Sounds like you have a blocked pipe, I feel your pain.
Can it be re-piped easily?

Not really as it is underneath a fully-tiled bathroom floor. I am also puzzled that two towel rails are not working (despite being in separate bathrooms), and there is a third towel rail in the same room as one of the cold ones which does work fine...

 

[terryplumb]

You could try removing the valve ,check the valve itself is ok and examine the pipe ,obviously you need to drain out as much as possible first. Is pipework microbore ( small diameter ,8 / 10mm)?

 

[KeenAmateurUK]

You could try removing the valve ,check the valve itself is ok and examine the pipe ,obviously you need to drain out as much as possible first. Is pipework microbore ( small diameter ,8 / 10mm)?

The copper pipes running to the valve are 15mm diameter. I did consider removing the valve, but I was a bit concerned that I'd fix the blockage and be faced with a torrent of water! I suppose I should drain down the whole system if I'm going to try that...! What do you think about a chemical cleaner?

 

[terryplumb]

Chemical cleansers won't do much ,if anything ,without circulation.
Did these cold radiators ever work fully ?
Is your system sealed / pressurised or fed from an F&E tank ?

 

[ianmcd]

No chemical cleaner or powerflush will clear a blockage, there has to be some flow for them to work

 

[KeenAmateurUK]

Chemical cleansers won't do much ,if anything ,without circulation.
Did these cold radiators ever work fully ?
Is your system sealed / pressurised or fed from an F&E tank ?

We've just moved into the property, but I distinctly remember the towel rail being hot (at least on the top half) during one of our visits. We've got an F&E tank in the loft. I haven't properly balanced the system yet, but I assumed that my problem is with the blockage, given that turning off all the other rads didn't work.

 

[terryplumb]

If no water comes through the valve ,either the valve is closed ,or blocked ,or the pipework is. Does the loft tank have a decent water level ?

 

[KeenAmateurUK]

If no water comes through the valve ,either the valve is closed ,or blocked ,or the pipework is. Does the loft tank have a decent water level ?

So the valve definitely opens - I can open/close it when the radiator is off and see the moving part, and closing it stops the few drops that build up. I went up to the loft last week and manually pushed the float down to make sure that there was plenty of water in there.

 

[ianmcd]

Find the cold feed where it connects to the system and see if a magnet attracts to the copper pipes in that area