you guys might want to wade through
this thread
a tad involved, but approaching a 'conclusion' (of sorts)
(I need to add today's 'lesson')
most (I would say almost all) of WCers' pump problems derive from too much restriction in the suction (pump inlet) line
- that's why the impeller 'lifts' and rattles, they suck air, etc
the pump is being blamed for what are in many systems simply hose configuration errors
- sort out the pump sypply before buying another
-> feed the pump with oversize hose, as big as you can fit