Phoenix Hard Water Guide

Is a water softener bad for plants in a Phoenix yard?

Softened water is kind to showers and kettles. Outside, on lawns, drip lines and pots, it is a different story.

Why softened water and Valley soil don’t mix

The University of Arizona Cooperative Extension’s turfgrass specialist, David Kopec, put it plainly in 2001: hard water is good for lawns and landscape plants, because its calcium and magnesium help counteract the sodium already in the water. A softener takes those two minerals out and puts sodium in.

That matters in Phoenix because the tap water starts with plenty of both. The City of Phoenix’s 2025 annual water quality report gives hardness of 10 to 17.6 grains per gallon and sodium of 91 to 183 parts per million. Kopec wrote that almost all lawns and shrubs tolerate Arizona drinking water as it comes. The trouble starts when softening removes the hardness and adds more sodium, about 8 mg per litre for each grain removed, according to the University of Nebraska–Lincoln Extension. Our page on how much sodium a softener adds works this out for each Valley city.

Will softened water kill grass? What Arizona’s turf specialist found

Will a water softener kill plants quickly? Kopec’s answer is subtler: the sodium itself may not harm the plants much, but it builds up in the soil and wrecks its structure. Soil with moderate to high sodium stops forming small clods and turns “dispersed and flaky”. Water then soaks in poorly, runs off, and roots are starved of oxygen.

So is soft water bad for grass? Over time, yes, through the soil. Nebraska Extension says repeated use of softened water on plants, lawns or gardens is not recommended. Alabama Cooperative Extension adds that it is not ideal for salt-intolerant plants. Desert landscapes on drip irrigation are no exception: the emitters wet the same small patch of soil every time.

Does your Valley hose bib or drip line get softened water?

That depends on how your home was plumbed. Some homes feed outdoor taps and the irrigation line from pipe that runs before the softener; others don’t. Don’t assume.

To check, test water from an outdoor tap and from the kitchen with hardness test strips. If the outdoor tap reads hard and the kitchen reads close to zero, your yard is on unsoftened water. If both read close to zero, the yard is getting softened water too.

Softener makers expect this. Pentair’s whole-house softener manual says the bypass valve should be used whenever you water outside for long periods, and WaterBoss’s manual says to use bypass mode for watering plants or lawns with untreated water. If your drip system runs off softened pipe, ask a plumber whether it can be fed from a point before the softener.

How to water Phoenix plants when you have a water softener

  • Use unsoftened water for the yard: an outdoor tap before the softener, or the bypass valve while you water.
  • Treat soil that has had softened water. Kopec recommends agricultural-grade gypsum twice a year on lawns, at 2.5 lb per 100 square feet, watered in. For trees and shrubs, including citrus, he gives 0.75 ounces per square foot of irrigated ground under the canopy. Gypsum takes months to work.
  • Flush salts from pots. Colorado State University Extension’s advice for house plants: water until it drains from the bottom, discard the drained water, and if a white crust forms, scrape it off with the top half inch or so of potting mix and rinse the pot through a couple of times.

Potassium chloride: the sodium-free option for Phoenix yards

A softener can run on potassium chloride instead of sodium chloride. NSF/ANSI 44, the standard for household softeners, covers both: the hardness minerals are swapped for sodium or potassium, depending on what you load. So potassium chloride avoids adding sodium to the water you pour on your yard.

There are trade-offs. Nebraska Extension says potassium chloride holds to the resin more strongly, so more of it is needed, and suggests asking a water treatment professional first. The University of Minnesota’s Water Resources Center puts it at 15 to 30 percent less efficient and several times the price of ordinary salt. WaterBoss tells owners to raise the hardness setting by 12 percent when they switch, and not to use it with iron or manganese in the water. Our guide to softener salt covers buying and loading it. To see how many bags a year your household would go through, work out your size.

Virginia Cooperative Extension warns that extra potassium in drinking water can be a risk for people with kidney disease and some other conditions. If that applies to you, ask your doctor first.

Removing salt from softened water: reverse osmosis and salt-free choices

Is reverse osmosis water good for plants? The sources we use don’t say so directly. What the U.S. Environmental Protection Agency’s WaterSense program does say is that reverse osmosis removes sodium and other dissolved minerals. It also sends five gallons or more down the drain for each gallon a typical under-sink system makes, so it suits a few pots, not a yard. Our page on reverse osmosis in Phoenix explains how these systems work.

Another option is to skip salt altogether. A salt-free conditioner adds no sodium, though it also doesn’t remove hardness.

Why California restricts some softeners, and where Arizona stands

California’s Senate Bill 475, passed in 2006, records that the Santa Clarita Valley Sanitation District found about one-third of the chloride in its wastewater came from home softeners that flush brine to the sewer. The district banned new self-regenerating softeners from 2003, to protect salt-sensitive crops such as avocados grown downstream in Ventura County. A second California law in 2009, Assembly Bill 1366, lets some local sewer agencies limit these softeners.

EPA WaterSense notes that some local jurisdictions restrict salt-based softeners, so check before you buy. We found no softener ordinance for Phoenix or other Valley cities. The City of Scottsdale says salt-based softeners add salinity to wastewater that normal treatment does not remove, and in 2014 it started a pilot rebate to encourage people to remove them. Its later removal rebate paid $125 a year for two years, with proof of removal each year; the last application window closed on March 31, 2025, and the city’s current rebate list no longer includes it.

Where these facts come from

Common questions

Can you water house plants with softened water?
Now and then, yes, but not as your regular water. Colorado State University Extension lists softened water as a source of salts in potting mix. Water pots from an unsoftened tap, water until it drains from the bottom, and throw away what collects in the saucer.
Is salt water bad for plants?
For many plants, yes. Alabama Cooperative Extension says softened water is not ideal for salt-intolerant plants, and cooler maker Seeley International says salty drain water should not go on salt-sensitive grasses or plants.
Will softened water hurt my citrus trees?
The University of Arizona's turfgrass specialist warns that softener sodium damages the soil that landscape plants grow in. Keep softened water off the drip line, and if it has been used, apply gypsum under the watered canopy at the rate he gives.
Why are some states restricting water softeners?
Because the salty water they flush into the sewer is hard to remove at treatment plants. In California, a 2006 law records that one sanitation district banned new self-regenerating softeners to cut chloride in a river used downstream for crops.