Hard Water and Water Heaters in Sacramento: What to Know
Scale is the quiet cause of many heater problems. Here is how it forms and what to do about it.
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The short answer
Hard water carries dissolved calcium and magnesium. When water is heated, those minerals come out of solution and settle as scale on heating elements and the tank floor. Scale acts as insulation, which makes a heater work harder, and it can shorten its life.
Hardness varies from one area and water source to another, and we do not quote a figure for your address, because it depends on where your water comes from. Your water provider publishes a water quality report, and a simple test kit gives you a number for your own tap.
How water hardness is described
The U.S. Geological Survey groups hardness into four classes, measured in milligrams per liter of calcium carbonate. One grain per gallon equals about 17.1 milligrams per liter.
| Class | Hardness, mg/L | What to expect |
|---|---|---|
| Soft | 0 to 60 | Little scale |
| Moderately hard | 61 to 120 | Some spotting on fixtures |
| Hard | 121 to 180 | Visible scale over time |
| Very hard | Over 180 | Heavy scale, heavier wear on heaters |
What scale does inside the tank
In an electric heater, scale coats the heating elements, so they take longer to heat the water and run hotter, which shortens their life. In a gas heater, a layer of scale and sediment sits on the tank floor between the burner flame and the water. The burner has to run longer, and the steel can overheat.
Noise is a common clue. A tank that rumbles or pops during heating often has scale and sediment on the bottom, with water trapped beneath it that boils and bursts through. A heater that runs out of hot water sooner than it used to may be losing capacity to that layer.
How to protect a heater from scale
- Have the tank flushed on the schedule in the manufacturer's manual
- Keep the thermostat at about 120 degrees Fahrenheit, which is the setting the U.S. Department of Energy suggests for most homes, since higher temperatures speed scale
- Ask a plumber to check the anode rod, the sacrificial rod that protects the tank from corrosion
- Consider a softener if hardness is high, see water softener installation
- Watch for rumbling, a rotten-egg smell or rusty hot water
- Replace the heater on time when it reaches the end of its life
Find your own hardness number
Look for your water provider's annual water quality report on its website. It usually lists hardness, sometimes as a range because water can come from more than one source through the year. For a number at your own tap, a hardness test strip from a hardware store or a certified lab gives you a result. If the number is in the hard range or above, scale is worth planning for.
Tank heaters and tankless heaters
Tankless heaters are also affected. Scale collects inside the heat exchanger and narrows the water passages, and it reduces flow and triggers error codes. Flushing with a descaling solution is the standard fix, and it should be done on the manufacturer's schedule. See tankless water heater service for how that works.
Tank heaters are more forgiving in some ways, since the scale mostly sits on the bottom, but a neglected tank can build up a thick layer that is hard to flush out. Regular maintenance is what prevents that.
When scale means replacement
A heavily scaled, aging tank may not be worth flushing. If a plumber tries to flush a very old heater and the tank starts to leak, the fittings and valves have been holding it together. Check the age first, and see whether to repair or replace for how to decide.
If you replace, ask about anode rods, isolation valves for future flushing and, in areas with harder water, whether a softener would extend the new heater's life.
Signs scale is building in your heater
- Rumbling, popping or crackling from the tank while it heats
- Hot water that runs out sooner than it used to
- Higher gas or electric bills for the same household use
- Cloudy or gritty hot water when you first open a tap
- White flakes in aerators on the hot side only
- Frequent tripping of the high-limit switch on an electric heater
Softener, filter or conditioner?
These three are often confused. A softener removes hardness minerals through ion exchange and needs salt. A filter removes particles and some dissolved substances but does not soften water. A salt-free conditioner alters how minerals behave so they scale less, but it does not remove them.
If the goal is to protect a water heater and fixtures from scale, a softener is the standard tool, and a conditioner is a partial one. Filtration solves a different problem, which our water filtration page explains.
Small habits that help
Do not turn the thermostat up more than you need. Every increase speeds mineral buildup and raises scald risk. Fix a dripping hot tap quickly, since dripping keeps fresh hard water flowing into the heater. And keep the manufacturer's manual where you can find it, since the flushing schedule and the anode rod details are in it.
Rentals and older heaters
If you rent, scale problems are usually the owner's to handle, since the water heater belongs to the building. Report rumbling, rusty water or a lack of hot water in writing, and include the heater's age if you can read the label. Owners can extend a heater's life with a flush and a check of the anode rod, and it is cheaper than an emergency replacement after a leak.
If you own an older home, ask a plumber about the age and condition of the heater during any visit. A quick look at the tank base and fittings tells a lot.
Questions about this topic
White crust on faucets, cloudy glasses and scale in a kettle are common signs. A test strip or your water provider's report gives a number.
It can. Scale insulates the heating surfaces, which makes the heater work harder and can lead to earlier failure.
Follow the manufacturer's manual. The right schedule depends on your water and how much you use.
The U.S. Department of Energy suggests about 120 degrees Fahrenheit for most homes. Lower temperatures also reduce scale and scald risk.
A softener prevents new scale. Scale already in the tank has to be flushed out.
Related guides
Repair or Replace a Water Heater? How to Decide
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Tankless vs Tank Water Heater: Which Is Right for You?
Tankless units last longer and save energy in many homes. They also cost more to install and can need a bigger gas line.
Water Heater Permit in Sacramento County: What You Need
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