towel

Though it's considerably less sanitary.

Submitter TurboJens explains this fix: The fill valve split in half and the floater does not cut off the water supply. The towel keeps the water inside and the wrench keeps it from overflowing.

"Our air conditioner was leaking through this pipe and flooding our laundry room and hallway. My husband's fix was to put a funnel under it, running onto a curtain rod, that then ran to a floor drain, with a towel under for added protection. In his defense, it worked beautifully."

Yup, he's a keeper!