Gilbert & Tempe Water Quality: A Side-by-Side Comparison

Gilbert and Tempe have the least hard water in the Phoenix metro — Gilbert at 11.5 GPG and Tempe at 10.0 GPG — but both still classify as "very hard" to "hard" and contain disinfection byproducts at 650-680x above health guidelines. "Best in the metro" is relative when the whole metro has challenging water.

These two cities are neighbors with different water systems. Tempe gets its water primarily from SRP surface sources and serves 185,000+ residents. Gilbert has grown rapidly to 280,000+ residents and relies on a mix of SRP, CAP, and groundwater, with quality varying across its rapidly expanding distribution zones.

Gilbert Water Quality

Hardness: 11.5 GPG (Very Hard)

Gilbert's water is the second "softest" in the metro behind Tempe, but at 11.5 GPG it's still well above the 7 GPG threshold for "hard" and more than double the national average. You'll still see scale buildup, though it accumulates more slowly than in Scottsdale or Mesa.

Key Contaminants

• HAA9: 41.0 ppb — 683x above EWG guidelines
• TTHMs: 32.5 ppb — 163x above EWG guidelines
• Chromium-6: 0.41 ppb — 14x above EWG guidelines

Gilbert's contaminant profile is somewhat less severe than Mesa or Chandler — notably absent are the high arsenic and vanadium levels those cities face. This is partly because Gilbert's water source blend is different and its groundwater wells tap into slightly different geology.

The Neighborhood Factor

Gilbert's rapid growth means water quality varies more than in older, more established systems. Newer neighborhoods in South Gilbert may receive water from different sources than the older areas near downtown. If you're in a newer development, your water could be better or worse than the city average.

Tempe Water Quality

Hardness: 10.0 GPG (Hard)

The "softest" water in the metro, though 10 GPG is still firmly in the "hard" category. Tempe residents will still experience scale buildup, just at a slower rate than their neighbors.

Key Contaminants

• HAA9: 39.2 ppb — 653x above EWG guidelines
• TTHMs: 31.0 ppb — 155x above EWG guidelines
• Chromium-6: 0.38 ppb — 13x above EWG guidelines
• Nitrate: 2.8 ppm — 8x above EWG guidelines

Tempe water testing has identified 34 contaminants, with 12 exceeding EWG health guidelines despite meeting all legal limits. The nitrate presence distinguishes Tempe from Gilbert — likely from agricultural and urban runoff in the area.

TDS: 350-500 ppm

Tempe's TDS range is lower than most metro cities, contributing to slightly better taste. But "slightly better" is relative — most people still notice the mineral content.

Side-by-Side Comparison

• Hardness: Gilbert 11.5 GPG vs. Tempe 10.0 GPG — both very hard
• HAA9: Gilbert 683x vs. Tempe 653x — both extremely elevated
• TTHMs: Gilbert 163x vs. Tempe 155x — comparable
• Chromium-6: Gilbert 14x vs. Tempe 13x — comparable
• Nitrate: Tempe 8x vs. Gilbert (lower) — Tempe has the edge here
• Overall: Very similar profiles. Tempe is slightly softer; Gilbert avoids high nitrate

Recommendations for Both Cities

Even with the "best" water in the metro, both cities warrant treatment:

• Water softener: Recommended at 10-11.5 GPG. You might get away with a smaller unit than what Mesa or Scottsdale requires, but you still need one.
• Under-sink RO: Strongly recommended for drinking water given the disinfection byproduct levels (650-680x above guidelines) and chromium-6.

Don't let "best in the metro" lull you into thinking filtration is optional. The bar is just very low.

Get a free test kit or book a free water test to see your home's actual numbers.