Radiator Pipe Sizing

[Gary]

Do these pipe sizes look reasonable?

I'm moving from a warm air system to a wet one and have the sizes of radiators required for each of the rooms (quote from plumbing co). I'm planning 22mm from the boiler teeing off to 15mm feeds for the front & back downstairs.

front 5.9kw (2.1+2.8+1) back 3.1kw (1+2.1)

For the upstairs teeing off the 22mm from the boiler with 15mm. front 3kw (1.4+1.6) back 2kw (1.3+0.7)

As you can see then it's 15mm to all the rads. Could there be a problem with sludge (low water speed) to the 0.7kw radiator in particular, or have I confused myself with all the Googling I've been doing, concerning

10mm pipe! I'm doing it all in plastic (except the boiler - Worcester Bosch 30cdi probably). Thanks Gary

[Christian McArdle]

It'll be fine. Just make sure you use inhibitor. Also consider running the pipework so that the heating can be easily subzoned. This way, you can run the downstairs heating at different times to the upstairs heating, which saves you money and is better for the environment.

Christian.