I have a combi boiler and every time I use it I have to use the valve until the water pressure gaige shows a safe level as every time I turn the boiler off it goes to zero. Is this a problem with the water board or my boiler?

Sorry I have no idea what you could be talking about, the domestic water side? Or the radiant heat part of the boiler? What pressure are you bringing it up to? When you say on and off do you mean at the stat? Or the power disconnect to the unit?