Question about the B&G series 100 pump: Is it possible for the pump to lose its ability to pump even though the motor is running fine? I am asking because my hot water circulation is no longer working and I have ruled out air lock and other obstructions. The pump just seems to no longer pump. It sounds fine - motor is rotating, the pump impeller and shaft are tight and strong (not sheared). There is some circulation, just very very slow. 4 hours to warm the pipes that normally took 5 minutes. The only thing different is that the pump body (where the impeller fits into) was badly rusted and pitted (since cleaned) and I think perhaps the impeller no longer is fitting snugly in order to create a "draw" and move the water into the impeller and sling it out the edges. Has anyone experienced this? I'm prepared to buy a whole new pump because I think part "p00351" is bad. I would replace it with the NRF-22 Very strange ... the pump is only 5 years old (cast iron) and worked normally only a few hours a day (morning showers).