The main cause of valves becoming stuck is when they are opened fully and left there. The correct way is to open them fully and then close them half a turn or so. This enables a little ‘wiggle’ room for the valve when it slowly becomes stuck again over the years. A valve stuck hard against the stops is very difficult to persuade to move again. On stuck valves I always use a penetrating lube the day before, WD40 or such like. Try a little gentle tapping around the valve …
