Central Heating Flush/Clean

Long Sean Silver

Hi Guys!

Not sure if this topic has been covered before. Apologies if it has. I have a fairly simple query (famous last words!).

I am in the middle of flushing out my central heating system. Fairly old (20 years) gravity fed system. I've drained the system by opening the valve at the bottom of my boiler, and stopping the ball-cock in the attic. I then released the ball-cock and let it flush through for about an hour. Nice clean water flowing, so no problem.

I now want to add some chemical cleaner. (and later some inhibitor)

2 questions,

1. How long should I leave the cleaner in the system? Can I leave it in a week? Is longer better? Is a week too long?
2. Is it better to turn the boiler on for a while? Will the chemicals in the cleaner work better with hot water, or is cold ok?

Thanks in advance!

Lenar3556

1. Depends on the chemical cleaner. For most of them a week would be fine. But follow the instructions.
2. Yes, for most cleaners temperature helps to breakdown sludge.

What you are planning wouldn’t be a very comprehensive flush vs what a contractor would do for you with a power flushing machine or magnetic filters. But if things aren’t too bad it will certainly help.

Definitely get plenty of inhibitor into it, it alone will make a significant impact even without the clerical cleaning.

10-10-20

And the other thing to do when flushing would be to close off all rads and then open one rad for a period and let the water through, then close it off and move to the next one. I was suprised by the amount of black residue trapped in each when I did this.