Readiness check

Is your water heater install ready for sizing, venting, and combustion air?

A water heater install fails on the pieces nobody wrote down: the demand it was sized to, the inlet the recovery was figured on, the vent category on the rating plate, and the air the burner actually gets. Skip the peak-hour demand and you buy a unit that runs cold in January; skip the worst-case draft test and combustion air check and you can leave a heater spilling carbon monoxide into an occupied room. This check confirms you have done the readiness items the sizing and venting guides call out before the unit is set and buried behind finish.

1. Do you have the building's peak-hour hot water demand for this occupancy, with diversity applied, before you pick the unit?Yes, peak-hour demand in GPH at the use temperature is documented for the occupancy with the right diversity factorRough estimate from fixture count or floor area, no occupancy peak-hour figureNo, sizing off tank gallons or matching the old unit

2. Did you take the cold inlet temperature for the coldest month and figure the temperature rise the recovery has to make?Yes, recovery was run on the coldest-month inlet rise to the setpointUsed an average or summer inlet, or the manufacturer's stated rise without checking local inletNo inlet temperature taken; recovery not checked against a rise

3. Did you read the rating plate and confirm the appliance venting category before touching the flue?Yes, category confirmed from the rating plate and vent material, size, and total height matched to that category and the manufacturer or tableAssumed the category from the heater type and reused the existing vent without confirming material and sizeNo, connected to whatever flue was there

4. Did you total the input of every gas appliance in the room and check confined versus unconfined space?Yes, added all gas appliance inputs and checked the room against the 50 cubic feet per 1,000 Btu/hr ruleChecked the water heater input alone, did not add the furnace or other appliances in the roomNo confined-space check done

5. If the space is confined, are two combustion-air openings in, high and low, sized on net free area for the source?Yes, high and low openings sized per source on listed net free area, not nominal duct or grille sizeOne opening, or openings sized off nominal duct size without accounting for grille or louver free areaNo combustion-air openings, or space is confined and openings were never added

6. Did you run the worst-case spillage and backdraft test with all exhaust running and the house closed up?Yes, closed the house, ran range hood, bath fans, and dryer, fired the heater, and confirmed smoke draws up the draft hoodChecked draft only with the room open or fans off, no worst-case conditionNo draft test performed

7. If a high-efficiency furnace vents out the sidewall, did you resize the flue for the water heater left on it?Yes, the flue was resized to the heater's input, commonly relined full height with a listed liner, and draft was provenNoted the oversized flue but left the heater on it, planning to watch itWater heater left orphaned on the old common flue with no resizing

8. Is thermal expansion and T&P discharge handled, with storage set hot and delivery tempered?Yes, expansion tank precharged to static pressure on the closed system, T&P discharge full size and unobstructed to an air gap, storage set at 140 degrees F and delivery tempered to 120 or below with a mixing valveSome pieces done, expansion control or the mixing valve or the T&P discharge not fully confirmedNo expansion tank on a closed system, or T&P discharge reduced, capped, or valved, or no mixing valve