How can I flush my central heating system?

find the drain cock on one of the lowest rads, stick a hose pipe on the end to the garden and open the valve.
when drained shut the valve and allow to refill and bleed rads.

thats a basic drain down and flushing out the old water. but if doing a flush because the system is fully clogged up you'll need to add a chemical.

hi-spec plumbing
August 2007