Tank Sizing

Notes

• The anode clearance is the measurement nobody takes. The rod is roughly 44 inches long and it lifts vertically out of the top of the tank, so replacing it wants about 97 inches of ceiling. In a basement with 7-foot joists on a tall tank, there is not room — and the anode is the single part that decides whether the tank lasts eight years or eighteen. Where the ceiling is low, buy a segmented rod at install time; discovering the problem later means draining the tank twice.
• A replacement tank is usually fatter than the one it replaces. The 2015 efficiency standards added insulation, and on tanks over 55 gallons they changed the technology entirely. A closet built around a 1998 heater frequently will not take its modern equivalent, and that surprise arrives with the old tank already drained and out.
• Measure the route, not just the space. 25″ across means the doorway, the stair turn and the pan all have to take it. An 80-gallon tank that fits the alcove perfectly and cannot get down the basement stairs is a wasted delivery.
• The T&P discharge pipe is not optional and it takes room. It runs from the valve down to within six inches of the floor, in rigid pipe, with no valve and no threaded end. Plan the route before the tank goes in — after it is in place, the run is awkward and it tends to get done badly.
• Short and lowboy tanks buy height by giving up something. They are wider, so the closet has to be wider, and a squat tank stratifies less well — the hot layer at the top is shallower, so usable draw before the water turns cool is slightly less than the gallon figure suggests.