Camco Blow-out Plug -
Blow-Out Plug removes water from lines for winterizing.
Screws into city water hose connection. Use compressed air to force residual water from lines as part of winterizing. USA.
Use to easily blow out water lines before winter storage
If your boat has a municipal water supply inlet, here is an easy way to clear the lines prior to winter layup. Just screw this fitting into the inlet, open all drains and faucets, then attach and activate an air pump. Plastic.