Tankless Water Heater in Tempe, AZ

How hard is Tempe water on a tankless heat exchanger?

Harder than average in parts of the system. Tempe's water quality report puts average hardness at 187 mg/L, about 10.9 grains per gallon, but lists a range from 9.5 to 29 grains per gallon. Most of the supply is Salt River Project surface water, joined by city wells and Central Arizona Project water and treated at the Johnny G. Martinez and South Tempe plants. Minerals drop out fastest where water is heated quickly, so a tankless unit in Tempe should have isolation valves for an annual flush, and homes at the harder end of the range may want a softener as well.

Will an older Tempe house need upgrades?

Often, at least a few. Tempe is a landlocked inner-ring suburb with a median build year around 1983, dense development in the north near Arizona State University and lower-density neighborhoods to the south. In a single-family house from that period, the heater is usually in the garage or a closet with a metal flue and a gas line sized for a tank. A gas tankless unit needs its own vent and frequently a larger gas line. In condos and townhomes, vent routes can be limited, which sometimes points toward an electric unit or an efficient tank instead.

What does Tempe require for permits?

The city's homeowner guide says separate plumbing and mechanical permits are required when applicable, and that repairs are exempt only when they don't involve replacing or rearranging valves, pipes or fixtures. A tankless conversion almost always changes piping, so expect to go through the Development Services permit counter at City Hall, 31 E. 5th Street (480-350-4311). The plumber usually handles the application and schedules the inspection. If the job also moves the heater to a new spot, adds a gas line or brings in a recirculation loop, mention it up front so the permit covers the whole scope and nothing has to be reopened later.

A Tempe note

Southwest Gas is the gas utility listed by the city. If you smell gas, leave the home first, then call 911 and Southwest Gas at 877-860-6020 from outside. Water emergencies on the city side, such as a main break, go to Tempe Water Utilities at 480-350-2837; a leak at the heater itself is a job for the plumber, so shut the cold supply valve above the unit while you wait.