Is microbore OK for combi

25 May 2007
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United Kingdom

I need your expert advice. I am trying to get my old system boiler replaced with a combi. THe problem lies with the radiators. My current system is piped in microbore (8mm copper I think). One heating company has advised (stressed!) that i replace all the microbore pipe and radiators due to the increase in pressure from a combi. Another has said thats not true and the pipe and rads will be fine with just a flush, so that the system is clean for when the combi is installed.

Do i really need 15mm pipe and new radiators??
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Thanks for your reply gasman1015. So how will they 'tap into' the microbore. Will they just reduce down from 22 to 15 to 8 or will they go 22 to 8mm straight away??
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They will just connect onto the existing flow and returns before it reduces down.... If you have twin entry rad valves these will need changing to a valve on each side of the rad

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