Quote:
Originally Posted by mtlakejim
Ok folks, I work in the oilfield and now knowing the full details of the plumbing system I understand that the only purpose for the check valve is to keep the pump from sucking air when your under normal operation.
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Maybe in the oilfield. Not in the RV. The check valve at the winterizing port actually works in the opposite direction preventing antifreeze from running out of the lines after winterizing, not preventing air from going in. And the 3 way winterize select valve isolates that line in the normal position so that the pump can’t pull air from that line.