Combi Boiler Hot water pipework

[bmpnorfolk]

Hi

A question re pipe runs for a combi. I'm fitting an oil fired combi to give stand alone dhw and ufh in my extension( dining room, 2 x bedrooms one e nsuite). Our water is very hard so obviously all supply will be via a softener with a drinking water untreated branch. I'll use a pro to connect and comission the boiler but I'm doing the donkey work of pipe runs etc myself. The dhw inlet and outlet to the boiler is 15mm. Given this should I

a) Go from 15mm to 22mm for the hot water pipe run and reduce to15 mm for the wash basin connections

b) Run all hot water in 15mm and just convert up for the connection to the bath tap.

In either case should I run the cold water in 15mm or 22mm to avoid problems with flow balancing at mixer taps ans shower?

Any other comments would be very welcome.

[Puddle]

Well it depends on what water supply you have into property,flow and pressure rate and flow rate of boiler,normally would be 15mm pipe work,if you have 22mm main coming in tee off and run cold to outlets and cold supply to boiler in 15mm and 15mm to hot outlets,if pipework bigger ,ie 22mm all you are left with is a lot of hot water being heated to sit in pipework when used
If you are getting in a pro to connect all up,get him in now,discuse,he can see property,probably knows area and advise from there

imho

[justlead1]

Hi. Although i have not fitted a water softener for many years i seem to remember high frictional resistance, which affects the flow rate quite dramatically, down stream of unit. This may influence decisions regarding pipe work sizing. I am sure there are others plumbers on here who trade in hard water areas with a greater knowledge of the subject. Good Luck