i have just had a grant vortex and a megalo fitted its been working fine up to a couple of months ago when we use the hot water tap and take hot water from the megaflo all is fine but once we turn the tap off hot water is dispersed out of the expansion core unit into the tundish outside this only occurs when the megaflo is filling is there any compertent meagaflo fitters out there that might have come across this problem