Thanks, that's what I feared. It does confuse me that the pump only has issues when it first starts up though, do you have any idea why that might be?
I reckon an unvented cylinder is what I'll go for when the time comes, although the flat does have a (mostly unused) gas connection so I'd also...
I've got a negative head pump fitted to my shower which isn't working properly. The system is as follows:
Hot water tank with integrated cold storage (combination tank/Fortic?)
Pipes from tank into loft, then down to pump
Negative head pump (Salamander Pumps 2.2bar)
Thermostatic mixer shower...