A water heater that has been drained and one that has not are, as far as moving it’s concerned, two different objects.
The arithmetic isn’t complicated. Water weighs a little over eight pounds per gallon. A common residential tank holds 40 to 80 gallons. So a 50 gallon tank is carrying roughly 415 pounds of water on top of its own weight, and an 80 gallon tank is carrying closer to 670.
What that means in practice
An empty 50 gallon tank is an awkward but ordinary two person carry. The same tank full is past what two people should be lifting at all, and well past what anyone should be lifting on a basement stair. The shape makes it worse: a tank is tall and round, so there’s nowhere good to grip and the weight sloshes while you move.
This is why draining comes first, every time. It isn’t a formality. It’s the difference between a routine pickup and one that shouldn’t be attempted.
Where these units tend to sit
Water heaters live in the least convenient parts of a house. Basements, garages, and utility closets, usually near a floor drain, often behind a door narrower than the tank is wide. The closet doorway is frequently the tightest point on the whole route out, and taking that door off its hinges is often the single thing that makes the job straightforward.
Before the pickup
Have the tank drained and standing clear, and have the path out of the room open. A drained tank with a clear route is a quick job. A full tank at the bottom of a stair isn’t a job at all until it’s drained.
