Verdict: Partly true. A softener removes the calcium and magnesium that leave scale in dishwashers, ice makers and other water-using appliances, but it isn't a filter, and how much it matters depends on how hard your water actually is.
Where the idea comes from
Hard water leaves white crust on dishwasher spray arms, faucet aerators and fridge dispensers, and much of Los Angeles County has moderately hard to hard water. Softeners are often sold as a whole-house fix, and "treated water" sounds like it should handle every water problem at once. It's easy to assume a softener also takes care of taste, odor and anything else in the water.
What the evidence says
Virginia Cooperative Extension's guide to household water treatment explains the trade-offs. It says hardness "may interfere with the cleaning action of soaps and detergents" and can cause scale buildup in hot water pipes, water heaters and plumbing fixtures. In a softener, sodium is exchanged for the calcium and magnesium, and the unit also removes small amounts of iron. The same guide cautions that "softened water can be more corrosive than unsoftened water," and it assigns taste, odor and chlorine problems to a different tool, the activated carbon filter. The guide is an older publication, but this basic chemistry hasn't changed.
Whirlpool gives a threshold for dishwashers. Its page on cleaning the dishwasher interior says a water softener is strongly recommended if your hardness is 15 grains or more.
Set that line against LADWP's 2025 Drinking Water Quality Report. Its source averages run from about 6 grains per gallon on Aqueduct water to about 14 on the Metropolitan Water District supplies, and the single highest readings, 280 mg/L at the Weymouth and Diemer plants, work out to about 16. In other words, every LADWP average sits under Whirlpool's 15-grain line, and only the peak readings in the Harbor and Eastern service areas cross it. Our post on whether refrigerator water filters soften hard water breaks the figures down by service area.
That's the core of the verdict. A softener does what it says on scale, but for many LADWP homes the manufacturer's own threshold doesn't call for one, and the softener brings trade-offs of its own.
What to do instead
- Get your hardness number from your utility's annual water quality report, in grains per gallon if your manuals use that unit.
- Read the water section of each appliance manual for a threshold, such as Whirlpool's 15 grains for dishwashers.
- Below the threshold, rinse aid, correct detergent dosing and regular descaling of steam appliances may be enough.
- If you go ahead, plan the plumbing first: a bypass for drinking and cooking water, and a check of any appliance that needs minerals.
- Keep using the refrigerator filter for taste and chlorine; a softener doesn't replace it.
Exceptions worth knowing
- •Sodium. Virginia Cooperative Extension says people on a sodium-restricted diet should consult a physician before using softened water, and that drinking and cooking lines can bypass the softener.
- •Corrosion. The same guide notes softened water can be more corrosive, which is worth discussing with a plumber or water treatment professional before installing.
- •Some appliances need minerals. A Wolf steam oven accepts softened water but not demineralized water. See whether to use distilled water in a steam oven.
- •Scale already in place stays put. Softened water going forward doesn't clean out a valve or heater that's already crusted; that part may still need service.
Sources
- •Virginia Cooperative Extension: Household Water Treatment (356-481) (what softeners remove; sodium; corrosion; carbon filters for taste and odor)
- •Whirlpool: Cleaning the Interior, Dishwasher (softener strongly recommended at 15 grains or more)
- •LADWP: 2025 Drinking Water Quality Report (hardness by source and service area)
The short version: A softener answers hardness and nothing else, and many LADWP homes sit below the line where a manufacturer asks for one.
Scale already slowing a dishwasher or ice maker is a repair question, not a softener one. TrueFix Los Angeles covers Westchester and the rest of the Westside; call (213) 787-3989.