According to the U.S. Department of Energy’s Energy Saver guide, most storage water heaters last 10 to 15 years, while tankless units can last more than 20. In Las Vegas, hard water can push a water heater toward the short end of that range.
One big reason is our water. With hardness around 16 to 17 grains per gallon, Las Vegas water carries a heavy load of calcium and magnesium, and heating it is exactly what turns those minerals into scale. Here’s how that wears down a water heater, the warning signs to watch for and the steps that help protect yours.
How hard water damages a water heater
The U.S. Geological Survey explains that when hard water is heated, solid deposits of calcium carbonate can form, which can shorten equipment life and raise heating costs. The Water Quality Association adds that calcium and magnesium salts are primarily responsible for most scaling in pipes and water heaters.
Inside a tank water heater, that scale settles as sediment on the bottom and coats heating elements. Rheem notes that this sediment acts like insulation, forcing longer heating cycles. Bradford White describes how water trapped beneath hardened deposits can boil, causing popping and rumbling, and warns that unaddressed mineral buildup strains components and can cause a unit to fail earlier.
Tankless water heaters aren’t immune. Instead of collecting sediment, they build scale inside the heat exchanger, which is why manufacturers call for periodic descaling.
What the research shows
The best-known test of hard water and water heaters was run by Battelle for the Water Quality Research Foundation. Researchers ran 30 water heaters on either softened water or very hard water at 26.2 grains per gallon, using an accelerated protocol. According to the published study summary:
- Gas tank heaters on hard water dropped from 70.4 percent to 67.4 percent efficiency over the equivalent of two years. Units on softened water stayed essentially constant.
- Tankless gas heaters on hard water fell from 80 percent to 72 percent efficiency and had to be delimed. After deliming they recovered only to about 77 percent.
- Electric tank heaters held their efficiency, but collected about 2 pounds of scale per year on hard water compared with a small fraction of that on softened water. The researchers expected shorter heating element life on hard water.
Las Vegas water is less hard than the 26-grain water in that test, so the effect here would be smaller. But the study’s own model ties efficiency loss to both hardness and how much hot water a household uses, and at 16 to 17 grains our water is still classified as very hard.
Warning signs your water heater is fighting scale
- Rumbling, popping or crackling sounds while the heater runs
- Hot water that takes longer to recover or runs out sooner than it used to
- White grit or flakes in faucet aerators and showerheads
- A tankless unit that loses flow or needs descaling more often
- A rotten-egg smell from the hot water only. The Las Vegas Valley Water District notes that the metal in some water heater anodes can react with naturally occurring sulfate, and that heaters left off for long periods can also develop this odor.
- Rust-colored water, moisture or leaks around the base of the tank, which call for a plumber right away
Maintenance that helps a water heater last
Regular maintenance is the cheapest protection you can buy. The DOE’s guide to choosing a water heater puts it simply: proper maintenance is key. That’s true for tank and tankless models alike. Always follow your owner’s manual, and call a licensed plumber if you aren’t comfortable working with scalding water, gas or electrical connections.
- Flush the tank. A.O. Smith’s maintenance guide says most tank water heaters need flushing at least once a year, and more often with hard water. Rheem’s flushing guidance recommends every six months for hard water. The DOE also suggests draining a quart of water every three months to remove sediment.
- Inspect the anode rod. This sacrificial rod corrodes so your tank doesn’t. A.O. Smith recommends inspecting it once a year and replacing it if it’s badly worn or several inches of core wire are exposed. Anode life depends partly on whether a water softener is installed, and Bradford White suggests asking your plumber about an aluminum anode if you add a softener.
- Descale tankless units. Tankless heaters need periodic descaling of the heat exchanger rather than flushing.
- Test the temperature and pressure relief valve. A.O. Smith says the owner should inspect it once a year and a professional every five years.
- Check the temperature setting. The DOE recommends 120°F, a temperature considered safe for most people.
If your heater is already near the end of its expected life and showing rust or leaks, maintenance won’t bring it back. In that case, plan for a replacement, and treat the water before the new unit goes in so it starts clean.
Stop the scale before it reaches the heater
Flushing removes sediment that has already formed. Treating the water reduces how much forms in the first place.
A whole-home water softener removes calcium and magnesium before water reaches your heater. In the Battelle study, heaters on softened water collected only a tiny fraction of the scale found in heaters on hard water.
If you’d rather not use salt, our ScalePrep salt-free scale control system keeps the minerals in the water while working to keep them from forming scale. An Arizona State University study for the WateReuse Research Foundation found that template assisted crystallization, a common salt-free technology, reduced scale formation by more than 88 percent on Colorado River water in accelerated testing. Results vary by product and water, so keep up with maintenance either way.
Your water heater isn’t the only thing at risk. Learn how the same minerals affect your plumbing in our post on scale buildup in pipes.
Frequently asked questions
How often should I flush my water heater in Las Vegas?
Manufacturers generally recommend at least once a year, and more often with hard water. Rheem suggests every six months for hard water. Check your owner’s manual for your model’s schedule.
Does a water softener affect my anode rod?
It can. A.O. Smith notes that anode life depends partly on whether a softener is installed, which is one more reason to inspect the rod each year. Ask your plumber whether a different anode material makes sense for your heater.
Is a tankless water heater better for hard water?
Not necessarily. Tankless units don’t collect sediment the way tanks do, but scale still builds up in the heat exchanger. In the Battelle study, tankless heaters on hard water lost efficiency and needed deliming. Treating the water helps both types.
Not sure where your home stands? Water Quality of Las Vegas is locally owned and offers a free water analysis with same-day service available and 100% financing. Call or text 702-623-2724 any time, 24/7, or contact us to book a visit.
