a bit nosier than normal.
why do they go faulty then, old age?
I have heard about them running dry as the system dries out, maybe due to blocked cold fed over time or system pressure lost beneath pump level.
What's the common way to spot a faulty or failing pump them? Just noise...
Might sound a strange question but what exactly are the bearings of a circulating pump (ie Grundfos 15-50) for? What's their job? How comes if they go water will pour out of the vent screw when removed??