Honda WX15T Owner's Manual page 44

STORAGE
4.Stop the engine, and allow it to cool.
5.Remove the pump drain plug, and flush the pump with clean, fresh
water. Allow the water to drain from the pump chamber, and then
reinstall the drain plug.
6.After the pump is clean and dry, touch up any damaged paint, and
coat areas that may rust with a light film of oil. Lubricate controls
with a silicone spray lubricant.
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PUMP DRAIN PLUG