I have a Main combi boiler and for the first time the low pressure error came on this morning, I returned the pressure to normal by turning the righthand key and closing it off again, but looking at videos though i believe the left hand key should be 'closed' at a vertical as well? I've never touched the left hand one so i presume its been like this since it was serviced a month or so ago, should i return it to the vertical position?