My central heating system has a separate hot water cylinder to store hot water, along with a red expansion vessel above it, typically around 1 bar. I only noticed the other day, but when using hot water, via a tap etc, the pressure can drop on the dial by around 0.2bar. Then when the heating is used or hot water is switched on, it typically settles at around 1 bar again when off. Is this sort of fluctuation normal? Thanks.
