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Old 06-14-2018, 06:46 AM   #2
JRTJH
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Join Date: Mar 2011
Location: Gaylord
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It's probably the port to ingest antifreeze into the trailer plumbing during winterization. Attach a short piece of hose, turn the valve below it to winterize, put the hose into a gallon of antifreeze, turn on the pump and it'll draw the antifreeze into the system.
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