Tankless Water Heater in Phoenix, AZ

How on-demand heaters work

When a hot tap opens, a flow sensor fires the burner or elements and water is heated as it passes through a heat exchanger. The U.S. Department of Energy says these units typically put out about 2 to 5 gallons per minute and last about 20 years. A household that runs several showers and appliances at once may need a larger unit or more than one.

Scale is the main enemy in Phoenix

The City's water quality report lists hardness of 10 to 17.6 grains per gallon. Inside the narrow passages of a heat exchanger, that mineral content forms scale that cuts flow and efficiency and can trigger overheating codes. Descaling flushes a mild acid solution through the unit using its service valves. Many owners pair a tankless heater with a softener or a scale-reduction filter to lengthen the time between flushes.

Signs your unit needs attention

• An error code on the display
• Water that turns hot, then cold, in the middle of a shower
• Lower hot water flow than before
• The unit shutting off when more than one fixture runs
• Loud operation or a burning smell from a gas model

Phoenix summers and incoming water

In the hottest months, water coming into the house can already be very warm, so a tankless unit has less work to do. In winter the incoming water is cooler and the heater has to raise it further, which is when an undersized unit shows its limits. Sizing should be based on the cooler months.

Installing or converting

1. Confirm gas line size or electrical capacity, since many units need more than the old tank did
2. Plan venting for gas models, often through a wall or roof
3. Install isolation valves so the unit can be descaled
4. Check whether a City of Phoenix permit is needed for gas or venting changes

What affects the price

• Gas or electric, and the unit's capacity
• Gas line, venting or electrical upgrades
• Indoor or outdoor mounting
• Whether this is a new install, a repair or routine descaling

Ask for a quote that spells out the equipment, the labor and any added work before anything starts.