Drain n refill Vented system

[imran999]

Wanting to flush out my hot water system and wondering, can i just drain out from the drain valve and leave it draining for 30 mins (refilling as it goes from the expansion tank?)

Would this flush fresh water through the whole system or will i need to open radiator valves?

Would add in x100 once the water has started running clear from the draining

 

[Best]

Just draining from the draincock will not flush water through the system.
The water will just find a straight path from the feed & exp tank down to the draincock. The water in rest of system pipework and radiators will mostly just stay there.
You would have to really drain down the entire system by shutting mains feed to exp tank and drain through from draincock and if any rads are piped from overhead, then drain each rad as well. Open rad vents to allow air in for water to drain out.

 

[steadyon]

Make sure the feed & expansion tank is clean before you start, otherwise you'll let any muck / sludge in there run through the rest of the system. Shut off water supply, empty F&E, clean, reconnect supply, drain as Best suggests.