Checck the Ball valve on the small Feed Tank in the loft if the ball valve is stuck and the tank is empty wiggle the ball valve arm up& down , water should flow and the tank should refill
www.elanar.co.uk, May 2009
Either there is no gravity where you live...or... when you get a call for hot water the boiler may or may not fire but not for long because perhaps the stat on the hot water tank believes the water is already hot enough?
Call for hot water turns the boiler on and tank stat satified turns boiler off.
