lockshield valve Turns but doesn’t open or airlock?

[MarkFS72]

So I’ve had a rad in the conservatory for years which the pipework is spurred from upstairs and it’s gone cold with cold pipes too for the first time. Expecting a simple fix I bled it, made sure the valves were open but no effect. So now I suspected a stuck valve (though both were kept open and turned freely) so to determine which one could have an issue I put a drain hose on (since this rad has a drain port between manual valve and rad), I closed the lockshield valve, opened the manual valve and opened the drain and got a flow until I shut the manual valve proving the feeed pressure and valve worked. Finally with the drain closed I opened the lockshield valve, kept closed the manual valve and reopened the drain and this time I got no flow.

Am I correct to conclude either that the lockshield valve is stuck closed, even though it turns and was kept open. Or that there is an airlock is in the return pipework which ascends 5’ before a 90 bend and T ing in upstairs? How do I prove an airlock and is there another method other than a full drain down to cure an airlock?

Or am I missing something?

 

[JohnD]

Turn off ALL the other radiators.

Does the cold one now heat up?

BTW the pipework plumbing is quite interesting. Who installed it?

 

[MarkFS72]

Forgot to mention I’d tried turning off the other rads in testing and it stayed cold. The only time it began warming was during bleeding and draining.

I was told he was a plumber, I wasn’t impressed with the kitchen sink install that he did either.

 

[terryplumb]

A lot of those braided ,flexible hoses are just not suitable for central heating systems, not to mention they look like a dogs dinner !
Is your heating system sealed / pressurised ,or fed from a small loft tank ?
The valve may be defective ,but I suspect it's more likely a blockage .

 

[Mottie]

Could it be that one of those hoses has collapsed internally?

 

[MarkFS72]

It’s a pressurised system. I suspect the feed flexi hose will be okay as hot water is getting in during testing bleeding and draining but the return hose is as yet untested.

 

[Mottie]

Why not close the working valve and loosen the connection to the suspected faulty valve to see if you are getting flow TO the valve first?

 

[MarkFS72]

I did do that but I loosened the the radiator side of the suspected stuck valve and it began leaking, should I have loosened the flexi side?

 

[Mottie]

Might be a bit more difficult being a sealed system. You are trying to find out if you are getting a good flow to (or away) from the suspect valve. You may have to let some water out of the system until it is no longer under pressure. Then, with the both valves closed, disconnect the suspect valve from the rad and put it in a bowl or bucket. It would help if you had an assistant at this point because you need to attempt to top up the system and see if water comes out of the suspect valve when you open it. If it doesn’t, repeat it with the hose off of the valve and see if you get flow from the hose to tell you which of those is at fault. That’s how I’d do it BUT I’m not a plumber so others may do it differently.

You haven’t got isolating valves at the other end of those flexi's have you?

 

[old duffer]

Could it be that one of those hoses has collapsed internally?

I'll take that bet with you! £100?

 

[MarkFS72]

No there’s no isolators.