Water Softener vs. Reverse Osmosis in Las Vegas

How each system works

Water softener: ion exchange for the whole house

A softener is installed where water enters the home, usually on the main line in the garage, so every faucet, shower and appliance gets treated water. Inside the tank, resin beads hold sodium ions. As hard water flows through, the resin trades that sodium for calcium and magnesium, as Penn State Extension explains. When the resin is loaded, the softener regenerates by rinsing it with salt brine and sending the captured hardness down the drain.

A softener is not a drinking water filter. Penn State points out that softening does not necessarily address more serious drinking water contaminants, and it does little for chlorine taste on its own. Our Las Vegas water softeners page covers sizing and control options.

Reverse osmosis: purified water at one tap

An RO system usually sits under the kitchen sink and feeds a dedicated faucet, and sometimes the refrigerator. Water passes through sediment and carbon prefilters, then pressure pushes it through a semi-permeable membrane that holds back dissolved salts, and a final filter polishes the taste. UMass Extension lists sodium, nitrate, lead, fluoride, sulfate and total dissolved solids among the contaminants RO reduces effectively. The Southern Nevada Water Authority (SNWA) notes RO is the only type of filter that removes the calcium and magnesium behind hard water.

RO is a point-of-use system by design. UMass Extension says treating all the water entering a home with RO is not practical. For a closer look at the stages, read what reverse osmosis is and how it works.

Water use, sodium and scale: the trade-offs

Water use

Both systems send some water down the drain. EPA’s WaterSense fact sheet says a typical softener uses 20 to 70 gallons per regeneration cycle. It recommends demand-initiated regeneration, which regenerates based on actual use instead of a fixed timer, and models that use 4 gallons or less per 1,000 grains of hardness removed. EPA also suggests installing a softener only where hardness tops about 10 gpg, a bar Las Vegas water clears easily.

For RO, EPA says a typical under-sink unit sends five or more gallons of reject water to the drain for every gallon it produces, while WaterSense-labeled systems must keep that to 2.3 gallons or less. In the desert, that efficiency difference is worth asking about.

Sodium

Penn State Extension estimates a softener adds about 7.5 milligrams of sodium per quart for each grain per gallon of hardness removed. At 16 to 17 gpg, that works out to roughly 120 to 128 mg per quart by our calculation. SNWA lists sodium intake as a potential drawback of softening and suggests people with medical concerns talk with their physicians. Two common answers: use potassium chloride instead of salt, or drink from an RO faucet, since RO reduces dissolved sodium.

Scale and the RO membrane

Hard water is hard on RO membranes, too. As one example, a manufacturer’s installation manual for an under-sink RO unit lists a maximum feed hardness of 10 gpg and warns that harder water can scale the membrane quickly unless it is softened first. A Water Conditioning & Purification article on extending residential RO membrane life likewise lists softened water as a way to reduce mineral scaling.

Which is right for you?

• Choose a softener if: your main complaints are scale on faucets and shower glass, spotted dishes, stiff laundry or a water heater full of mineral buildup.
• Choose reverse osmosis if: your main goal is better drinking water, you are tired of buying bottled water, or you want to cut dissolved solids and sodium at the tap.
• Choose both if: you want scale protection throughout the house and purified water at the kitchen sink, a common combination with Las Vegas Valley hardness.
• Consider salt-free scale control if: you want to avoid salt entirely. SNWA notes salt-free systems condition water rather than soften it, so expectations should match.

Hardness varies somewhat by water provider across Las Vegas, Henderson, North Las Vegas and Boulder City. Look up your area with our water hardness by city tool, or read the full Las Vegas hard water guide. Homes on private wells should be tested on their own.