Turns out there’s a pipe in old-fashioned (“big ol’ tank”) water heaters that brings fresh cold water in through the top and down to the bottom of the tank where it is to be heated. It should then rise (recall your grade school physics lessons) to the top where it enters the hot water pipes supplying the house. The way water heater makers get us to buy new water heaters every ten years, now that tanks don’t rust out as reliably as they once did, is to make that pipe out of a white plastic that starts breaking down just a few months after the ten-year warranty expires.
