Water Heaters in Arizona: Tank vs Tankless, Hard Water and Yearly Care

Most Arizona homes have either a tank water heater or a tankless one, and both need a little yearly attention because our water is hard. Flush a tank once a year, descale a tankless unit on a schedule, keep the thermostat around 120 degrees, and plan for a replacement once a unit gets to roughly ten years old.

Buyers want to know how old the water heater is, and sellers wonder whether it will raise questions. Here is what I tell people about caring for one in the Valley.

Tank or tankless: the basic difference

A tank heater keeps a large insulated tank of water hot around the clock, and it is still the most common type. A tankless heater warms water only when you open a tap. Southwest Gas, the gas utility for much of the Valley, says tankless units are often expected to last 20 years or more, while it suggests thinking about replacing any water heater that is 10 years old or older. Those are utility figures, so treat them as a guide and not a promise. How long yours lasts depends on the water, the care it gets and the installation.

The same utility notes that water heating can account for a meaningful slice of a home's energy use. That is one more reason to look at the heater when you compare homes, not only the air conditioner. If you are weighing AC age and efficiency too, my post on replacing your AC in Arizona covers that side.

Why hard water matters here

Phoenix-area water carries a lot of dissolved minerals. Those minerals settle out as scale and sediment, and a water heater is where they collect first. In a tank, sediment builds on the bottom and can cause rumbling or popping noises, lower efficiency and corrosion. In a tankless unit, scale coats the heat exchanger. I wrote about what hardness does to a house in Hard Water in Phoenix, and the water heater is the first place most owners see the effects.

A simple yearly checklist for a tank heater

Rheem, a major manufacturer, recommends a short routine for tank models, usually once a year: flush the tank to clear sediment, inspect the anode rod and replace it if it is worn or heavily coated, test the temperature and pressure relief valve by briefly lifting its handle, and look for leaks at the top, base and fittings. Rheem also notes that the anode rod and relief valve are often jobs for a licensed plumber, and that do-it-yourself maintenance can affect a warranty depending on the manual. Check yours before you start.

What a tankless unit needs

For tankless models, the same manufacturer suggests at least one service a year. That includes cleaning the inlet filter, flushing the heat exchanger with a descaling solution, checking the vents and testing the relief valve. With hard water, it suggests flushing about every six months. Since this is a Valley with hard water, a tankless unit that has never been descaled is something I point out to buyers.

Set the thermostat and insulate

Southwest Gas says 120 degrees is comfortable for most households, and Rheem recommends staying between 120 and 125 degrees to limit scald risk and energy use. Insulating the tank and the hot water pipes can help reduce heat loss, but on gas units keep the burner access and air intake uncovered.

Warning signs it is time to call a pro

Rheem lists several signs: less hot water or slow recovery, water temperature that swings, popping or rumbling noises, rust-colored or cloudy water, a rotten-egg smell, moisture at the base, visible corrosion, or an energy bill that jumps with no change in how you use hot water. A leak at the base of a tank usually means it is near the end of its life, so do not wait on that one.

Buying or selling a home

If you are buying, find the heater's age on the label and ask when it was last flushed. Your inspection can flag problems, and my inspection period guide explains how the BINSR process works. If you are selling, an older heater is worth looking at before listing, since it is one of the things buyers ask about. You can see how I help sellers on my selling page, or start with the buying page.

Questions people ask

How long does a water heater last in Arizona? There is no single number. Southwest Gas suggests considering replacement at 10 years or older for a standard unit and cites 20 years or more for tankless, and hard water makes regular maintenance more important here.

Should I flush my water heater every year? Manufacturers such as Rheem recommend flushing a tank about once a year to clear sediment, and flushing a tankless unit about every six months in hard water. Check your owner's manual first.

What temperature should I set it to? About 120 degrees works for most households according to Southwest Gas, and Rheem recommends 120 to 125 degrees to reduce scald risk.

Is a tankless water heater worth it? It can be, but it still needs descaling in hard water. Ask a licensed plumber about your home's layout and gas or electric setup before deciding.