15mm into 22mm into 15mm into 22mm heating

[VictorianHomeOwner]

I have a a 3 story house with a combi boiler on the top floor and a crawl space under ground floor. The heating on the ground floor is rubbish and looking under the floor the pipes are a bodged mess of 15mm copper, 15mm plastic, 10mm copper and 10mm plastic, that is uninsulated and slowly leaking. So I just want to replace the ground floor piping for 6 big radiators.

The question - The heating circuit comes into the ground floor crawl space as 15mm copper. Can I/should I attach this to 22mm and run it round the ground floor with short runs of 15mm copper to the radiators. Or should I just use 15mm copper because the top 2 floors are all 15mm copper and the ground floor is at the end of the circuit?

Thanks

 

[Scott_D]

It depends on the heat output required but sounds like you need 22mm from the boiler to the ground floor.
What boiler do you have?
How many radiators in total?

 

[SimonG]

22mm from boiler, 6 big radiators wont run effectively off of a 15mm supply. From memory, 13000 btu is 15mm maxed out.