Back pressure does make a pump louder.. As does air.. And I agree about the starting and stopping thing. I built my mother that watercooled system (MicroStealth) last mother's day with a Rio 180, did the same for a friend last summer. They both run their systems 24/7 day in and day out, and both of their pumps are happy as ever without a hickup. (Haven't changed the water in either one yet either, and they're both running aluminum/copper combined..
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