Now I'm in the DUH category. I know about this concern, but isn't that "fill your glass w/ toilet TANK water, which is potable water?" This wouldn't backsiphon toiler BOWL water, would it? How could it? Kurt, Now that you're gonna start looking in the tanks, you'll be amazed at what is growing in some of them...mold, scum like you wouldn't believe. THAT is what you'd be drinking with a cross-connection. And, you'll be amazed at how many "short" fill valves are installed by homeowners when the original valve fails, creating a cross-connection. Also, anyone with thoughts on those tanks where the low-profile white fill valve is mounted to the bottom of the tank? If that ain't a cross-connection, what is? Thanks Jerry! You said it.