Stop me if this has been posted before.
Jennifer and Jim kept getting huge water bills. They knew beyond a doubt that the bills weren't representative of their actual usage, and no matter how they tried to conserve, the high bills continued. Although they could see nothing wrong, they had everything checked for leaks or problems: first the water meter, then outdoor pipes, indoor pipes, underground pipes, faucets, toilets, washer, ice maker, etc. -- all to no avail.
One day Jim was sick and stayed home in bed, but kept hearing water running
downstairs. He finally tore himself from his sick bed to investigate, and
stumbled onto the cause of such high water bills. Apparently this had been happening all day long when they were not at home. Knowing that few would believe him, he taped a segment of the 'problem' for posterity