Two Radiators Cold

Deryck Tintagel · 16 Nov 2019

I have been reading up on the possible cause but I am not sure on what path to take.

The system is vented and has not had work done on it. Piping is run in 15mm (?) plastic.

I have the radiators in the hall and downstairs loo stone cold. The flow and return pipes are cold. The radiators had been working but I think the one in the loo was getting progressively cooler last winter.

The radiator in the loo has a lockshield and TRV, but the hall has a wheelhead and lockshield valve as the room stat is in the hall. I have checked the hall radiator and the valves are open. I have not yet checked the TRV in the loo yet.

Is this an air lock or pipe blockage? I would like to change the radiator in the loo (and also in the bathroom) so would this be an opportunity to add a cleaning agent to the system, drain and refill? I would like to know that the radiators were fully working before I do this.

TIA

Terrywookfit · 16 Nov 2019

If there is no flow to the rads then adding any cleaner is pointless.
Disconnect rads and check there is a good flow from both pipes.
Also check it is a barrier pipe by reading the printing on the pipe

denso13 · 16 Nov 2019

Close down all the other radiators and see if they heat up any better. You could leave only one of the non working ones open and try them one at a time.

foxhole · 16 Nov 2019

Replacing the rads will give you the opportunity to flush the system. Trying to solve problem before replacement is pointless.

Terrywookfit · 16 Nov 2019

foxhole said:
Replacing the rads will give you the opportunity to flush the system. Trying to solve problem before replacement is pointless.

Trying to flush a radiator with no flow to it is also futile !

foxhole · 17 Nov 2019

Terrywookfit said:
Trying to flush a radiator with no flow to it is also futile !

He will be replacing faulty/ blocked rads not flushing them .

Madrab · 17 Nov 2019

Have you tried to bleed the rads? Once bled do you get a constant and sustained flow of water when you shut down each end?

Terrywookfit said:
Disconnect rads and check there is a good flow from both pipes.

I'd certainly start at that point before getting replacements unless it's just for aesthetics- refer back to the first sentence

foxhole said:
Trying to solve problem before replacement is pointless.

Have to disagree, if the rads are being replaced regardless then fair enough, take the old ones off and buy new ones ready to replace, but I'd certainly be testing/solving the flow problem first. May be nothing at all to do with the rads.

Deryck Tintagel · 18 Nov 2019

Madrab said:
Have you tried to bleed the rads? Once bled do you get a constant and sustained flow of water when you shut down each end?

I'd certainly start at that point before getting replacements unless it's just for aesthetics- refer back to the first sentence

Have to disagree, if the rads are being replaced regardless then fair enough, take the old ones off and buy new ones ready to replace, but I'd certainly be testing/solving the flow problem first. May be nothing at all to do with the rads.

Answers to the questions so far:

I have tried bleeding the rads and get just an expected trickle of clear water

The rads are to be replaced for aesthetics as the current ones are quite rusty along the bottom edge and for the cost to replace it is better than painting them. However, based on experience I think it best to have something fully working before changing parts just in case a new fault is introduced. I was considering a flush as I have been in the house 11 years and some are warm but not evenly and some need balancing

I assume that shutting off the TRVs on the other rads is sufficient? To check flow from the pipes can it be done without fully draining the rad - inlet and bleed valves shut no air can get in?

Thanks for the replies so far - I might have the other half happy with a warm loo soon

Madrab · 18 Nov 2019

OK, if the rads are coming off anyway then shut off both ends and drain, if one end has a TRV that will turn to 0 then fine. If the lowest setting is a frost symbol then you will need to cap the valve with a 15mm stop end cap when removed.

Drain and remove the rads, then check them for blockages. Best way to do that is get them outside and blast a hose through them. Best way to clean the rad out is up on end with the rad tail opening sitting on a damp cloth, fill the rad up and then move it off the cloth and let the water run out. Watch your feet/legs. Then turn it upside down and repeat, keep doing this it runs clear.

Then back to the rad valves and open each into a bucket and ensure a good flow.

If your other rads are suffering from cold spots etc then if they can't be manually flushed outside then ideally they will need powerflushed, a normal mains pressure/gravity flush may help but it won't clean the rads out properly.

sircerebus666 · 21 Nov 2019

Normally the issue is a stuck pin on the trv.

Quick check to do is unscrew the head of the trv and pull up the pin with pliers

Op - are the two rads on the same pipework run and do you have any isolation valves fitted?

Deryck Tintagel · 21 Nov 2019

sircerebus666 said:
Normally the issue is a stuck pin on the trv.

Quick check to do is unscrew the head of the trv and pull up the pin with pliers

Op - are the two rads on the same pipework run and do you have any isolation valves fitted?

I haven't had the time to fiddle with the rads yet, but I would guess the two cold rads are somewhere on the same pipework run as the hall rad is on the loo wall and the loo rad is about half a metre from that. I wouldn't know it there are any isolation valves - I would guess not and they had been working for 10 years previously.

I will see if I can have a go at looking for an air lock this weekend

sircerebus666 · 21 Nov 2019

Check the trv while you're at it , takes seconds to unscrew and pull up the pin , no draining down or anything like that

There's a good chance a 10 year old trv is stuck and needs replacing

denso13 · 21 Nov 2019

sircerebus666 said:
Normally the issue is a stuck pin on the trv.

The hall one doesn't have a TRV according to the OP.

Terrywookfit · 21 Nov 2019

Drain the rad and connect a hose to each valve in turn. There should be a full flow from both pipes.
Do it with a hot system to see if both get hot.

sircerebus666 · 21 Nov 2019

denso13 said:
The hall one doesn't have a TRV according to the OP.

You're right , but I am unsure how they have been plumbed in , one faulty trv could be affecting both

Plus it's a 10 second job to check and I like to check the simple things first before I start pulling rads off walls

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Two Radiators Cold

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