I obviously wasn't clear enough. I noticed it first in the shower, but it is systemic throughout the house. Kitchen faucets, tub spigots, shower heads all blast cold water, but hot water just seeps out, barely enough to initiate the shower head.
The tank was built at the same time as the house. I'm assuming that it's just a builder grade quality. I've never ****ed with this except to light a pilot, so I'm out of my element, but I can try a few of these suggestions on Tuesday.