No hot water pressure

[Lehman]

I have had a relatively new hot water system (less than a year old) and we have had a gradually developing problem with hot water pressure. the system is a standard gravity fed system with a cold tank in the loft and the hot water cylinder directly underneath. We have recently only been able to get 1 bath of hot water before the hot water pressure goes and only a dribble comes out of all hot taps in the house. The cold water pressure coming out of the same cold water tank appears unaffected.
Up until yesterday we have been able to leave the system overnight and the pressure returns to normal. we do hear some strange sounds from the hot water tank that sound like large air bubbles being released in the tank. Yesterday we struggled to get one bath full of water out before the pressure went and we are still without hot water pressure. If you leave the tap off for a few minutes then you do get adequate pressure from the hot tap but only for a few seconds and then the pressure dies again. Does anybody know what this may be caused by and if there is a simple solution???

 

[rjm2k]

If it's under a year old, isn't it still under warranty?

 

[Lehman]

It is but BG being BG are taking their time coming out. I was hoping there was something I could do or at least be armed with a bit of knowledge to be able to discuss the issue with the BG service guy when he turns up

 

[rjm2k]

Have a look inside the large cold tank when the hot is slow, is it full? Are you sure the cold tap you tested is from the same tank, is it also slow when the hot is slow?

 

[Lehman]

At work at the moment so can't check the cold water tank, however, the cold appears unaffected even when the hot runs slow. We are positive that the cold taps we are testing are from the same tank as it took us a long time to convince BG how we wanted the pipes to be run when they installed the system (the house was renovated and it's listed so we had significant restraints over where pipes could go!!!!)