Replenish the air supplies of the chambers?

[nameisme]

Hello all,

I sometimes get a knocking sound coming from the pipes. It normally starts of slow then gets faster and then gets slower and slower again until it then stops. Lasts about 10 seconds and then sometimes just totally random with no rythum. Seems to happen when hot water is being used in the house from either them rads or the taps.
What does it sound most likely to be?
Also I was thinking of replenishing the air supplies of the chambers to see if it helps.
But how long do I keep all the taps open once I shut off the water supply? I read until the water has all gone from the house but how would I know this?

 

[Madrab]

Ok, unfortunately, most of your post makes no sense.

Knocking sounds from the pipe could be water hammer, possibly loose pipework or water pressure too high.

If you are talking about a megaflo unvented then you need to open the lowest HW tap, once that stops then use the T&PRV to drain the cylinder until that stops, the instructions will be on the side of the cylinder or in the instruction manual.