Possible plumbing error

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I have an issue with a cold/luke warm radiator in my new loft conversation and I think it might have been plumbed in wrong. I should add the plumber was kicked off the job and then I was abandoned by the builder so I had to finish things myself.
The pictures show where a different plumber connected to pipes that were left for him and as far as I can see the pipes, 6 in total are for hot and cold water and 2 radiator circuits.
I believe it has 2 circuits because the 1st plumber had a non-TRV bathroom radiator in mind so may have plumbed the bathroom rads separately?
The 2nd plumber though has just connected both circuits in parallel or possibly intended to and that is what I think might be my issue? I’m wondering if one of the rads is now on a circuit with either 2 feeds or 2 returns. Rather than break open the plasterboard wall can anybody suggest the best way I can test for this as I can access all the pipes from the airing cupboard. My hot & cold water work ok , 2 of the radiators work ok. Of the other 2 radiators one is cold but eventually gets Luke warm and the other has yet to be connected.
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Last edited:
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I have added some labels of how I believe the current plumbing flows....

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Turn off all radiators at their TRV ( don't touch their lockshield valves).

on the radiator that is not heating , make sure both it's valves are fully open ,and it is bled of air.

Run central heating and see if problem rad now heats fully.
 
I fitted stop valves to all the pipes before I fitted the radiators so I can isolate them easily. I have already bled and fully opened the lockshield on the problem rad but I will try shutting the others off and report back, thanks.
 
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Open all the isolation valves ,except any with open pipework.
 
Open all the isolation valves ,except any with open pipework.
Of the 2 working radiators, the bathroom one doesn't have a TRV and another in the walk in wardrobe has a TRV. I balanced both by gradually reducing the flow by closing up the lockshield valves to the point where they still get nice and hot but I have tried running with all 3 radiators "fully open" and the problem one still does not get hot. I considered bridgeing the pipe stubs on the remaining radiator position, the one that has no rad fitted to see if that would get hot or not but I'm struggling to get my head around any rads could get hot the feeds and returns have been paralelled up incorrectly?
 
As said ,you need to close ALL rads down except one. Any without a TRV ,close one of its valves ,just make a note of how many turns it takes to close , so you can return it to its original position later.
This will concentrate the pumped circuit through your problem rad.
And if it heats up will prove the plumbing to it is correct.
 
Sorry, I was getting confused, I'll shut the 2 working ones off and see if the problem one gets hot.
 
If the stop valves you fitted to the pipes are the ordinary "screwdriver slot" isolation valves, then:
1. You have already reduced the flow to the radiators as these are not full bore valves.
2. They are highly likely to leak in time. They are generally not designed for the constant high temperatures of central heating.
 
I used them for a smidge over 20 years on my previous heating system with no issues which is why I used them again. Being able to remove a rad without dropping the water out etc has proved very convenient given how disjointed my build was up until the builder gave up and walked. This is only one of ten rads that's not warming up and it is"geographically" at least not the last on a circuit so I doubt the valves are reducing flow is an issue.
The reason I suspect the plumbing circuit to be wrong is because the work done by the plumber, before getting kicked off, was shocking. The plumber that installed my Air source heating took pity though and sorted out quite a lot at no extra charge.
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As said ,you need to close ALL rads down except one. Any without a TRV ,close one of its valves ,just make a note of how many turns it takes to close , so you can return it to its original position later.
This will concentrate the pumped circuit through your problem rad.
And if it heats up will prove the plumbing to it is correct.
Terryplumb, after shutting off the two working radiators and commanding the boiler to heat, the non working radiator did not warm up.
 
Terryplumb, after shutting off the two working radiators and commanding the boiler to heat, the non working radiator did not warm up.
Then it's either not plumbed in to flow and return pipes ,or you have an air lock,or your pump isn't upto the job. I assume when you removed the rad in question ,that you allowed water to flow out from both valves ,for several minutes whilst keeping pressure topped up to around 1.5 bar ?
 
I assume when you removed the rad in question ,that you allowed water to flow out from both valves ,for several minutes whilst keeping pressure topped up to around 1.5 bar ?
I have previously removed the radiator to check water is able to flow out of the valves and bled it again once re-fitted if that amounts to the same? The bathroom radiator is on the same floor and further away from the pump so it is looking like I might have to open the wall up to see how the problem rad is connected. Thanks for your advise though.
 
You can't see from the picture but the problem radiator is almost directly above where the pipes go through the ceiling and the bathroom and wardrobe rads about 10 feet further away...
 
Problem solved!
I connected the two pipes together that go to the bathroom without a rad fitted yet, opened the stop valves and the problem rad in the loft conversion got hot straight away!
I’m thinking the original plumber hooked the two radiators in series with each other rather than parallel across the feed and return. Obviously this means it is still plumbed incorrectly as the water from the first rad will have cooled before it gets to the second but as the second rad is only a four inch bit of pipe, cutting open the wall can wait for now and if they are hot enough once the second rad is fitted, I might leave it as is.
I have sketched how I think the two circuits may have been intended and how I think they actually ended up. Thanks again for help and comments.
 

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