Tempe's water report lists hardness averaging about 10.9 grains per gallon, but the range runs from about 9.5 up to 29, so homes in different parts of the system can see very different scale. A softener sized to a test at your own tap is the reliable fix. Call the number on this page to be connected with a local plumber in Tempe.

How hard is Tempe's water, really?
The City of Tempe Water Utilities Division reports average hardness of about 187 mg/L, or 10.9 grains per gallon, with a range of 163 to 500 mg/L, which is about 9.5 to 29 grains. Most of the supply is Salt River Project surface water from the Salt and Verde watersheds, joined by city wells and Central Arizona Project water, treated at the Johnny G. Martinez and South Tempe plants. Because the blend shifts, the average can understate what one home sees. Test at the tap before choosing equipment.
Will a softener fix the taste too?
No. Tempe disinfects with chlorine, using sodium hypochlorite, and keeps a residual near 1 mg/L. A softener removes hardness and does nothing for that taste. If taste or odor bothers you, a carbon filter on the main or a drinking water unit at the kitchen sink is the right tool. Some owners in Tempe want both, and the plumber can stage them in one install.
Does my older Tempe house need a permit for this?
Tempe's median home dates to about 1983, so plenty of houses were built before softener loops were common. Adding one means cutting into the main, installing a bypass and running a drain line. Tempe's homeowner permit guide says separate plumbing permits apply when work is more than a simple leak repair; repairs are exempt only when they don't replace or rearrange valves, pipes or fixtures. Ask the plumber to confirm with the Community Development permit counter at City Hall before the job. The city also notes that lead in tap water comes mainly from private service lines and home plumbing, and it's identifying private service line materials, so an older house is a good candidate for a look at its supply line while the plumber is there.
One local note
If a water line breaks while the softener is being installed or serviced, Tempe Water Utilities has a customer support line for water emergencies at 480-350-2837. For the softener itself, the plumber should test at your tap rather than rely on the citywide average; a home near the top of Tempe's range needs a much larger setting than one near the bottom, and setting it too low brings the spotting right back.
Water Softeners & Filtration questions in Tempe
Why does hardness differ from one part of town to another?
How do I turn ppm or mg/L into grains per gallon?
Will softened water raise the sodium in what I drink?
Is a reverse osmosis faucet worth adding with a softener?
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