Mystery cold radiator. Please help!

[Musicaldave]

Hi everyone. I moved into a new house last year and I have one cold radiator. It’s the furthest from the house, in an extended part of the dining room.

When we moved in we needed to replace the boiler as it was on its last legs. But still it was cold.

So I bought and fitted a new rad, in case it was sludged up. But still it was cold.

My third plumber told me the house needed to be balanced. And that in order to do so - given the valves were old, was to replace the valves and add TRVs to the whole house. In his words he said ‘in my career there’s never been a radiator I couldn’t fix with balancing.

Needless to say, it’s still cold. And I’m £750 lighter.

Any ideas on what could be the problem? The rad can get hot, if you drain it. But as soon as the system is depressurised it will cool. Freezing at the bottom. Very luke warm at the top. The return pipe always stays cold. The flow warm.

I asked the plumber if the return pipe could be blocked and whether we could flush air / water / powder to try to clear it. But he says microbore won’t survive that and the joints could blow across the whole system.

So I’m stuck. Because it’s an extension it’s simply too cold to be a useful room without a working rad. And replacing the pipe work would be a lot of work because it’s buried in a flat roof and exterior walls.

Any thoughts welcome!

Thanks. Dave.

 

[BILLENK]

If you turn all rads off except that one and it still doesn't get hot and if your flow is hot at the valve I'd lean towards a blocked return.

Worse even being microbore a kinked pipe.

You could try a powerflush with chemicals in a couple weeks before but it's a risk you take money wise as if that that fails you'll be looking at tracing and replacing pipework.

 

[king of pipes]

Seems like you have a blockage in the pipework to this rad , isolate the valves, drain and remove the rad attach a hose to one of the valves and fully open it check there is a flow of water coming out if you have a combi open the filling loop if its vented then let it run till it runs clear isolate and you will need swap to the other valve and repeat if this does not work you will need a engineer. Cheers kop

 

[SimonG]

What size pipes in the extension?

 

[townfanjon]

Usual microbore cockup probably , lift the floorboards and check no numpty has teed off another rads pipes .

 

[Best]

If the flow is really hot getting to valve, it can still be the flow virtually completely blocked, but just slight flow through it.
Simple to have each pipe to the rad checked to see if water can flush through them, as others methods state.
Then, if flow good, you might have a faulty valve which allows flow in one direction only, so return valve (if ordinary valve) could be broken inside, - but that is rare.
I bet your pipework is overloaded, although you still should get some heat in rad if it is.
Radiators added on to systems on extensions, conservatories and roof conversions tend to be done by greedy idiot builders by themselves, or they use an idiot who poses as a heating engineer

 

[Musicaldave]

Hi. Thanks for the replies.

To answer a few questions:

It’s 8mm Microbore throughout.
The flow pipe is fine. If you disconnect the rad hot water will flow fine from it.
The rad only got luke warm at the top when every other rad is turned off.
If you drain the rad you can pull the hot water through and it will get hot. But when the system is represurised it will cool again.
The rad is never cold at the top. But maintains some luke warmth.
Floor is concrete so not really an option. Would have to pull down the ceiling and expose the exterior wall pipe work to replace it.

Do you think my plumber is right about microbore not being able to take a flush with air / water / powder. I imagine even a small improvement on a blockage could work wonders? He paints a picture akin to the hull of the titanic blowing if you force water through microbore. Blockage could be highly likely on return pipe. But I think a kink is less so. No work has been done in the last few years that could cause a kink, and the radiator did - I’m told by the previous owner - once work. Presumably pipes don’t kink unless physically damaged inadvertently by works?

Finally, is the only option to dig out the pipes and replace? In practice if that’s the case I think I’ll just have to sadly replace it with an electric heater as the decorative costs on top of the plumbing would be astronomical.

I’m sure I’m being dumb but there’s no way to bypass the return like old single pipe Systems did?

Thanks again.

 

[Best]

Your micro bore pipes can be flushed, but mustn’t be put under high pressure because they are soft copper.
Just a matter of opening a valve at the problem radiator and if water can flow from it, then use the filling loop at boiler to keep flushing through it, as a post already said. But keep watching that pressure doesn’t raise much (say less than 1 bar max) at boiler gauge.
Best done with a couple of people - one at filling point and the other person watching the flow from outlet. Or get heating engineers in.

 

[Riley]

Am I missing the point do you get good flow at both rad valves with the rad removed?

 

[king of pipes]

Have you flushed the return pipework and got a good flow of water ? Also take the radiator outside and flush that out with a hose. Kop

 

[Musicaldave]

Thanks again for the replies. The rad is new so it’s not a problem there. The flow is fine on the flow pipe if you take the rad off. No we haven’t tried forcing water / air / powder through the return pipe - which is what I think might fix it - because my plumber says it’s just as likely to blow joints throughout the whole system given it’s microbore. I’ve seen a few vids on YouTube where people even just pump air from a tyre pump through a blocked pipe and a load of grime dislodges down.

I’m just trying to gauge why my plumber won’t do this and whether I should get someone else in. Cheers.

 

[Riley]

!!!!!!Is there water at the return pipe!!!!

 

[Musicaldave]

Hi. I don’t know that I’m afraid as I wasn’t there when the plumber took it off. Thanks.

 

[Riley]

Well that’s another prime test if you’ve water at flow and not return then you may have a blockage on return

 

[Musicaldave]

Hi. Yes. It seems almost certain that it’s a blockage on the return. As it’s the only thing we haven’t tried. Question is what we can do about it. Plumber says microbore won’t tolerate pressured water / air through the return pipe to try to block it. And it’s not feasible to replace the pipe work. Thanks.

 

[Best]

Your plumber sounds like an idiot.
Both pipes should have been flushed.
The micro bore could be pressure flushed as well, but just having a limited pressure

 

[Riley]

You can flush microbore just carefully. What sort of boiler have you got?

 

[Musicaldave]

Hi. It’s a combi main - part of the Baxi group. Thanks.