Central heating system cleaning

[Happyharry]

Hi all, I have added a bottle of Fernox F3 into my towel radiator upstairs, I have run the heating for a good few days now.
I have bleed off points downstairs I can attach a hosepipe to drain the system.
Question when all the water has drained out can I leave the hosepipe on and fill the system so the water flows through the system and remove any left over crap out of the hosepipe, and then when I see water running clear remove hosepipe, and then fill up the system and bleed all the radiators.
Many thanks

 

[Chuck]

The risk with leaving the drain open is that you'll only flush a limited fraction of the pipework because the water will follow the path of least resistance. Better, IMO, to close the drain, refill, circulate to get water forced around everywhere then drain fully and refill.

Manufacturer's instructions are here:

Cleaner F3 500ml - Fernox UK

Cleaner F3 is an effective, universal pH neutral, non-foaming liquid cleaner, which removes sludge, scale and debris from existing central heating systems to restore heating efficiency and eliminate boiler noise. When commissioning new systems in accordance with BS 7593:2019 regulations and best...

fernox.com

best to follow them to the letter, they're the experts.

 

[Jerry]

The risk with leaving the drain open is that you'll only flush a limited fraction of the pipework because the water will follow the path of least resistance. Better, IMO, to close the drain, refill, circulate to get water forced around everywhere then drain fully and refill.

Manufacturer's instructions are here:

Cleaner F3 500ml - Fernox UK

Cleaner F3 is an effective, universal pH neutral, non-foaming liquid cleaner, which removes sludge, scale and debris from existing central heating systems to restore heating efficiency and eliminate boiler noise. When commissioning new systems in accordance with BS 7593:2019 regulations and best...

fernox.com

best to follow them to the letter, they're the experts.

If you are paranoid, refill, circulate and drain a couple of times......