Identifying flow pipe to radiator when the radiator is removed

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Hello,

I have a new radiator to fit that requires the flow feed to enter via a specific valve on the radiator. Sadly I failed to make a note of which pipe is which before draining the system and removing the radiator.

Does anyone know of a way to identify the pipe without reattaching the old radiator and filling the system? The pipes are completely hidden in the cavity wall so I can't think of an obvious way round this problem.

Thanks
 
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Make a temporary link between the two pipes, eg short length of speedfit) turn both valves on, and feel which pipe gets hot first when you turn heating on.
 
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Thank you both, I really appreciate you taking the time to respond.

I remember which side the drain off valve was on. Am I right to think the flow would be on the opposite side?
 
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How are all your other rads plumbed in? If the flow is on the left, chances are that that one will be the same.
 
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Am I right to think the flow would be on the opposite side?
Unfortunately no. You'll have to trace the pipework or refit the radiator or pipe as above, to check properly.
 
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If you have access to a known flow (another rad would do, or after the boiler) and a compressor you could run compressed air (set regulator to 1 bar max) up the flow and see which pipe the air comes out of (you'd need to turn all other radiators off, isolate boiler, isolate hot water cylinder if you have one, isolate any ufh or other heat circuits).
if you do this, beware- even in a drained system there's probably black water still in pipes which will make a right mess if it fires out uncontrolled.
 
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Thank you both, I really appreciate you taking the time to respond.

I remember which side the drain off valve was on. Am I right to think the flow would be on the opposite side?
Maybe, but it may have been "reverse-plumbed" originally.
 
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If you have access to a known flow (another rad would do, or after the boiler) and a compressor you could run compressed air (set regulator to 1 bar max) up the flow and see which pipe the air comes out of (you'd need to turn all other radiators off, isolate boiler, isolate hot water cylinder if you have one, isolate any ufh or other heat circuits).
if you do this, beware- even in a drained system there's probably black water still in pipes which will make a right mess if it fires out uncontrolled.

Or just connect f and r with a bit of pipe, quiche refill and test. Will be quicker and less risky
 
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Hello,

I have a new radiator to fit that requires the flow feed to enter via a specific valve on the radiator. Sadly I failed to make a note of which pipe is which before draining the system and removing the radiator.

Does anyone know of a way to identify the pipe without reattaching the old radiator and filling the system? The pipes are completely hidden in the cavity wall so I can't think of an obvious way round this problem.

Thanks

There is no short cut, really. However, on the assumption that both valves will be 15mm so interchangeable, take a punt on one side and fit rad. Once refilled and turned on, you will know wether you won the 1:1 bet.

If you lose, DD again and swap valves
 
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There is no short cut, really. However, on the assumption that both valves will be 15mm so interchangeable, take a punt on one side and fit rad. Once refilled and turned on, you will know wether you won the 1:1 bet.

If you lose, DD again and swap valves
Def the safest approach :)
 
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Hi all,
I'm back at the property tomorrow and will have a go at identifying the flow pipe through a temporary connection.

Thank you all for your input it's genuinely amazing!
 

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