Skip to content

City water profile

Antioch water quality

Compare local ZIP estimates, evidence quality, associated public systems, and compliance history for Antioch, California.

Median indexed hardness

223PPM

2 indexed ZIPs

Range 221–225 PPM

State comparison
34 PPM above
State hardness rank
#64 of 242
Matched utilities
1
Active health records
0

City summary

What the indexed records say

Antioch has 2 published ZIP profiles across Contra Costa County. The indexed median is 223 PPM, compared with 189 PPM across California.

Among the 242 Californiacities with an indexed median, Antioch ranks #64from highest to lowest. Across all 678 state ZIP profiles, available estimates run from 3.3to 728.5 PPM.

The 221–225 PPM range shows how much the available ZIP estimates vary within the city label.

Hardness distribution

How local ZIP estimates compare

Soft0 ZIPs
Moderately hard0 ZIPs
Hard0 ZIPs
Very hard2 ZIPs

2 of 2 ZIP profiles have a hardness estimate. Bars count ZIP profiles, not households or laboratory samples.

Evidence quality

Distance, dates, and confidence

Median nearest distance
9.2 miles
Profiles with evidence
2/2

Confidence labels

High: 0Moderate: 2Low: 0

Observation window: Jan 13, 2016 to Jun 3, 2026.

ZIP directory

Water reports in Antioch

Open a ZIP for site-level provenance and measurements.

ZIP code

94509

Very Hard

221 PPM

Nearest site
7.8 mi
Confidence
Moderate

View full ZIP evidence →

ZIP code

94531

Very Hard

225 PPM

Nearest site
9.2 mi
Confidence
Moderate

View full ZIP evidence →

Public water systems

Utilities associated with this city

City Of Antioch

PWSID CA0710001

Surface water
System population served
115,074
Last reported
Jun 22, 2026

The system names this served city; Census place overlap links the city to this ZCTA.

Compliance history

What EPA records show

No active health-based violation appears among the associated systems in the represented EPA reporting quarter. This does not mean every contaminant was tested at every tap.

No violation records are included in the current lookback window.

Practical next steps

Move from index to evidence

  1. 1. Open your ZIP. Check distance, dates, confidence, and the associated utility.
  2. 2. Read the current CCR. Confirm source water, detections, limits, ranges, and notices.
  3. 3. Test the tap when needed. Confirm health concerns or treatment sizing with the right method.

Questions people ask

About water in Antioch

Is the water hard?

The indexed city median is 223 PPM. Open the ZIP report to verify the distance and confidence behind that estimate.

Is the tap water safe?

Compliance history is utility-wide and cannot guarantee conditions at every tap. Check current notices and test when address-specific evidence is needed.

Do I need treatment?

Choose treatment only after confirming the problem at the property. A softener targets hardness; contaminant treatment requires a matching, verified performance claim.