Radiator comes on when hot water on

Hi all,

Looking for some advice...i have noticed that when our hot water is running, three radiators upstairs come on. Can anyone give some advice on what this could be? And if I get someone to fix it, how much would it cost?
It' literally three radiators coming on. The rest of the radiators are cold.
Thanks in advance

 

have you got a hot water cylinder?

Look for one of these, probably near the pump and cylinder, might be near the boiler

https://www.screwfix.com/search?search=port+valve

for the moment, turn off the radiators (just finger tight, no great force)

 

Thank you for your help. It's a combi boiler...just thought it's so strange that only 3 radiators come on

 

The make/model of your combi would help.

 

Get your boiler manual (or download it..)... check which the ‘flow’ pipe is - coming out your boiler. Turn it off using the isolator. Try and recreate the issue.

Sounds like a diverter valve to me - probably worn over the years. It may be servicable but good chance its just a replacement... which may/may not require the system draining.


Cost - probably £80 or so labour and the cost of the valve - depends on boiler type and ease of replacement.

 

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