Turn on a tap in the Phoenix metro and you get hard water. The City of Phoenix's 2025 water quality report lists total hardness of 172 to 302 parts per million across its system, about 10 to 17.6 grains per gallon. The city calls it harmless to drink, and notes that it can leave scale in pipes and water heaters.
West Valley cities such as Goodyear, Buckeye and Surprise run their own water systems, and many homes around Tonopah draw from wells. Each utility publishes a yearly report with its own hardness numbers, so check the one for your address.
What scale does inside a tank
Calcium and magnesium drop out of the water as it heats. In a tank heater they settle on the bottom as sediment, and you hear them as popping or rumbling while the burner or element runs. That layer sits between the heat and the water. Your heater burns more gas or power for the same shower, and the bottom of the tank runs hotter than it was built for.
What it does to a tankless heater
A tankless unit heats water as it flows through a small heat exchanger. Scale narrows those passages. You notice lukewarm water, swings in temperature, or an error code on the display. Manufacturers call for descaling at least once a year, and more often in hard water. Your unit's manual gives the interval for your model.
Flush the tank once a year
Most manufacturers recommend draining and flushing a tank water heater about once a year. A flush pushes the loose sediment out through the drain valve before it sets hard. While the tank drains, we check the drain valve, the relief valve and the anode rod, the metal rod that corrodes so the tank doesn't.
Our Rattle Membership includes a yearly water-heater drain and flush.
A softener takes the load off
A water softener pulls the hardness minerals out before the water reaches the heater, the fixtures and the pipes. If you already have one, keep the salt topped up and the settings matched to your water. Replacing a water heater is a good time to ask whether a softener makes sense for your home.
When to call
Call if the heater rumbles, the hot water runs out sooner than it used to, the water comes out rusty, or you find water around the base of the tank. Reach us at (623) 707-3869.
More about our water heater service.
