Flushing a water heater in Las Vegas: 16-grain water, sediment and the anode

How fast sediment builds on 16-grain valley water

The Las Vegas Valley Water District’s water quality summary, published in 2026 with 2025 data, lists total hardness at 280 parts per million, or 16 grains per gallon, with calcium at 75 and magnesium at 24 parts per million. Henderson’s own water quality page puts the city’s water at about 304 parts per million (18 grains).

No maker publishes a pounds-per-year figure for a heater, because the rate depends on more than hardness. A. O. Smith’s electric use and care guide (2022) says sediment builds faster or slower with water quality, hardness and the temperature setting, which is why it wants the first flush six months after installation: what comes out tells you how quickly your own heater collects it.

The best real-world measure we found comes from another desert city. A University of Kentucky Cooperative Extension fact sheet (revised 2001) reports a New Mexico State University study in Las Cruces, where heaters that had run for 5 to 15 years on untreated hard water held from 3.86 to almost 40 pounds of scale and sediment. More on what valley minerals do around the house.

Water heater flush sediment: the steps

These steps follow A. O. Smith’s draining guide and Rheem’s flushing article. If your manual says otherwise, it wins.

1. Turn the heater off: the breaker for an electric model, the gas control to OFF for gas. A. O. Smith suggests a few hours’ head start so the water can cool.
2. Open a hot tap and let it run until the water is no longer hot.
3. Shut the valve on the cold water line feeding the heater.
4. Screw a garden hose onto the drain valve at the base, and send the free end outdoors, to a floor drain or into a big bucket.
5. Let air into the tank by opening a hot tap somewhere in the house. Rheem lifts the pressure relief valve lever for the same purpose.
6. Open the drain valve. A. O. Smith says most tanks take 20 to 40 minutes to empty.
7. Once it’s empty, reopen the cold supply with the drain still open. Fresh water stirs up the grit on the bottom and carries it out; keep going until the hose runs clear.
8. Shut the drain valve, unscrew the hose and refill the tank with a hot tap open, so trapped air escapes.
9. Restore power or gas only once water flows steadily from that tap. A. O. Smith is firm that an electric heater stays off until the tank is completely full.

If nothing comes out of the drain valve, sediment may be blocking it. A. O. Smith’s advice is to call a plumber or service technician rather than force the valve.

A water heater sediment flush kit is optional on a tank: the steps above need only the hose and the heater’s own valves.

How often: what Rheem and A. O. Smith say

Rheem’s flushing article (2026) recommends once a year for most homes and every six months where water is hard. A. O. Smith’s website says at least once a year, and more often in hard water areas. The table puts each valley area’s published hardness against those rules, with the tankless interval alongside.

The anode rod, in hard water and in softened water

A tank heater’s anode rod is a sacrificial metal rod: it corrodes so the steel tank doesn’t. A. O. Smith’s electric guide calls it a consumable item, not covered by warranty, and says it must stay installed at all times or the warranty is void. Its schedule is to inspect the rod at the first six-month flush and then at least once a year.

On untreated valley water, that yearly check is the baseline. Softened water changes it: the same guide says that if you use a water softener, the anode rod will deplete faster than normal, so inspect it more often and replace it as needed. Rheem’s maintenance article (December 2025) adds that checking the anode once a year can add years to a heater’s lifespan.

Does a softener protect the heater?

Against minerals, yes. In the Las Cruces study, heaters on softened water held 1.09 to 4.27 pounds of scale, against up to almost 40 pounds for the hard-water group, and the hard-water heaters needed more energy to deliver the same hot water. The extension fact sheet expects longer life for water heaters in a softened home.

The cost is the anode. With softened water there is little sediment to flush, but the rod wears faster, so the yearly maintenance visit becomes an anode check more than a flush. If a softener is on your list, size one for your household first, and read how salt-free systems differ before treating them as the same.

Tankless flushing note

A tankless heater has no tank to drain. Minerals form scale on its heat exchanger instead, and the fix is a descale with vinegar or the maker’s solution, pumped through the service valves. Noritz’s limited warranty (2025) excludes damage from water harder than 12 grains per gallon, so valley water at 16 is already past it. Whether your tankless water heater flush is in Summerlin, Henderson or anywhere else on valley water, the steps and the warranty questions are on our page about tankless heaters and hard Las Vegas water.

For how long a tank lasts and what hard water takes off it, see hard water and water heater life in Las Vegas.

Sources for this page

• Las Vegas Valley Water District · water quality summary · 2026 (2025 data) · hardness, calcium and magnesium.
• City of Henderson Department of Utility Services · water quality page · 2026 · typical hardness of 304 ppm (18 gpg).
• Rheem · flushing article (2026) and maintenance article (2025) on its website · flush intervals, steps, signs of sediment, yearly anode checks.
• A. O. Smith · draining guide on its website (undated) and electric water heater use and care guide (2022) · draining steps and time, flush schedule, rate of sediment, anode rod and softened water.
• University of Kentucky Cooperative Extension Service · fact sheet on softening hard water · 2001 · New Mexico State University study of scale in heaters on hard and softened water.
• Noritz · limited warranty · 2025 · 12 grains per gallon hardness exclusion.