Across the water systems that serve Hilmar, California, Arsenic has appeared in EPA compliance samples — standard municipal treatment targets this contaminant, though detections in the compliance record indicate it has reached household taps at measurable levels.

Data: EPA SDWIS, CCR Reports, ECHO Last verified: 2026-06-04

Arsenic in Hilmar Tap Water

Arsenic has been detected in Hilmar, California drinking water at a maximum level of 9.8 ppb — below the EPA MCL of 10 ppb.

This analysis covers 7,862 residents across 1 ZIP code in Hilmar.

Hilmar's overall water quality grade is A (95/100).

Is Arsenic in Hilmar Water Safe?

Arsenic was detected in Hilmar water but currently falls within EPA limits. However, some health organizations argue the EPA MCL may not be protective enough.

If you are concerned, a reverse osmosis filter can reduce arsenic levels further.

Arsenic Levels by ZIP Code

Average arsenic level across Hilmar: 9.8 ppb

Health Effects of Arsenic

• Increased risk of skin, bladder, lung, and kidney cancer
• Cardiovascular disease and type 2 diabetes
• Skin changes (darkening, thickening, lesions)
• Developmental effects in children exposed in utero

Health risk severity: High. Governed by the Arsenic Rule (2006).

How Arsenic Gets Into Drinking Water

• Natural deposits in rock and soil (especially in western U.S.)
• Runoff from orchards and glass/electronics production
• Historical use of arsenic-based pesticides
• Well water in areas with arsenic-rich geology

What to Do About Arsenic in Hilmar Water

1. Install a reverse osmosis (RO) system certified under NSF 58
2. Adsorptive media filters (iron-based) can also reduce arsenic
3. Have well water tested if on a private supply
4. Boiling water does NOT remove arsenic — it concentrates it

Look for filters certified under NSF 53 / NSF 58 for arsenic removal.

Related

• Arsenic — National Overview
• Arsenic in California
• California Water Quality
• Hilmar Water Quality
• Check Your ZIP Code