If something holds water, it stands up to scrutiny. It isn't full of holes like a swiss cheese.

Water is one of the more persistent and pernicious forces in the universe: if there is a hole -- or even a tiny flaw -- in your roof or one of your water pipes, the water will eventually find its way through. Moreover, the "quick and easy" patches are usually ineffectual, or don't last for long: the only definitive fix for a leaky pipe is to disassemble, clean, and properly reassemble the pipe; practically the only definitive fix for a leaky roof is a whole new roof.