A tank water heater lasts about 10 to 15 years and a tankless unit more than 20, according to the U.S. Department of Energy. How long does a water heater last in Los Angeles specifically? Usually toward the short end of that range, because most of LA County runs moderately hard to very hard water, and the minerals in it are what wear a tank out.
The call usually starts with a puddle in the garage or a cold shower before work. And the first question is almost always the same: is it worth fixing, or is it done?
The answer depends on two numbers. How old the heater is, and how hard your water is.
How Long Does a Water Heater Last in Hard Water
Not as long as it would elsewhere. Hard water shortens a water heater’s life because the minerals in it drop out when the water is heated. Calcium and magnesium settle to the bottom of a tank as a layer of sediment, the same white crust you see on a showerhead, only thicker.
That layer sits between the burner and the water. On a gas heater the burner has to run longer to push heat through it, and the steel underneath runs hotter than it was designed to. On an electric heater, scale builds on the lower element until it burns out. Either way, the tank works harder every year, and the bottom is where tanks usually rust through.
Tankless units don’t hold a tank of sediment, which is why they last longer. But scale still forms inside the heat exchanger, so in hard water they need regular tankless descaling and service to reach that 20-year mark.
How Hard Is the Water Where You Live
It depends on your neighborhood, more than most people expect. The U.S. Geological Survey classifies water hardness as soft up to 60 mg/L, moderately hard from 61 to 120, hard from 121 to 180, and very hard above 180. The City of Los Angeles gets water from several sources, and LADWP’s latest water quality report shows how different they are.
| LADWP service area | Main sources | Average hardness (2025) |
|---|---|---|
| San Fernando Valley | LA Aqueduct, local wells, MWD Jensen plant | 103-140 mg/L, moderately hard to hard |
| Central Los Angeles | LA Aqueduct, local wells | 103-116 mg/L, moderately hard |
| Western Los Angeles | LA Aqueduct | 103 mg/L, moderately hard |
| Eastern LA and Harbor | MWD Weymouth, Diemer and Jensen plants | 140-236 mg/L, hard to very hard |
So a heater in Eagle Rock or Highland Park can be living with up to twice the minerals of one in Westwood. In the Valley, neighborhoods like Sun Valley and Tujunga sit in the middle of the range.
Outside the City of LA, your own utility publishes the same numbers. Burbank, Glendale, Pasadena and Santa Clarita each put out an annual water quality report, and hardness is listed in it.
How to Tell How Old Your Water Heater Is
Look at the label on the side of the tank. Many list a manufacture date outright. If yours doesn’t, the date is hidden in the serial number, and the format depends on the brand. Home inspectors keep brand-by-brand decoding guides, but two common ones cover a lot of LA garages:
- A. O. Smith (newer units): the first four digits are year and week. A serial starting 1604 was built in the 4th week of 2016.
- Rheem: the first four digits are month and year. A serial starting 0815 was built in August 2015.
Check the date before it fails. If your tank is past 10 years, get a replacement price now, while you can compare options instead of buying in a hurry with water on the floor.
Signs It’s Near the End
Age tells you when to start watching. These tell you it’s close:
- Water around the base of the tank, or rust on the bottom seam
- Rust-colored or metallic-smelling hot water when the cold water runs clear
- Popping or rumbling when the burner fires, which is sediment
- Hot water running out faster than it used to
You can also see the sediment for yourself. Attach a garden hose to the drain valve at the bottom of the tank, run it to a floor drain or the yard, and let a few gallons out. Be careful, because that water can be well over 120 degrees. If it comes out cloudy, gritty or full of white flakes, the tank is carrying a load of minerals. Flushing once a year is the single best thing you can do to reach the long end of the range.
If the tank itself is leaking, shut the cold water valve on top of the heater and call. That’s not a repair, and the emergency line is answered around the clock.
Repair or Replace
Repair makes sense when the tank is sound and the part is the problem. Replacement makes sense when the tank is the problem, or when it’s old enough that you’d be fixing it again soon.
| Situation | Usually the right call |
|---|---|
| Under 8 years, no hot water or a pilot that won’t stay lit | Repair the part (thermocouple, gas valve, element or thermostat) |
| 8 to 12 years, first problem, tank dry | Repair is fine, but start planning |
| Any age, water leaking from the tank body | Replace. A corroded tank can’t be patched |
| 12+ years in hard water, any repair needed | Replace. The next failure is close behind |
Honestly, a lot of calls are the first row. A thermocouple or a heating element is a small job, and we’ll tell you when that’s all it needs. We carry the common parts and the common tank sizes on the truck, so most fixes and most replacements happen the same day.
Making the Next One Last
A new heater in the same hard water will age the same way unless the routine changes. Flush a tank once a year. Have the anode rod checked every few years, because it’s the part that corrodes so the tank doesn’t. On a tankless unit, schedule descaling once a year.
And if your heater is over 10 years old and showing any of those signs, get a flat-rate price before it picks the day for you. Call Hard Hat Rooter and Plumbing at (855) 331-7788, and check our current coupons first.
