Replace 8mm microbore with 15mm on Bathroom radiator

16 Jul 2009
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United Kingdom
Hi All, this is my first post.

My house built in late 1996 has 15 mm copper pipes going to all upstairs radiators but as the 15 mm flow and return pipes approach each radiator it reduces down to 8 mm microbore. Is there any technical reason for this i.e. flow rate / pressure, balancing the system :?:

The reason I ask is I’m about to replace a small 500W bathroom radiator with a 732W towel radiator plus TRV and lockshield. I’d rather plumb the new radiator in with 15mm copper or 15mm pushfit i.e. not re-use the existing 8mm microbore. Thus can I just remove the 8mm sections and replace with 15mm or is this not a good idea.

Thanks in advance :D
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Thats may need to balance the system afterwards as the water will take the path of least through 15mm rather than 8mm

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