Water quality records for Castle Rock, Colorado show Nitrate detections on file — a finding that places it among the contaminants worth tracking for this area.

Data: EPA SDWIS, CCR Reports, ECHO Last verified: 2026-04-05

Nitrate in Castle Rock Tap Water

Nitrate has been detected in Castle Rock, Colorado drinking water at a maximum level of 8 ppb — below the EPA MCL of 10 mg/L (as nitrogen).

This analysis covers 99,741 residents across 3 ZIP codes in Castle Rock.

Castle Rock's overall water quality grade is C (68/100).

Is Nitrate in Castle Rock Water Safe?

Nitrate was detected in Castle Rock 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 or ion exchange filter can reduce nitrate levels further.

Nitrate Levels by ZIP Code

Average nitrate level across Castle Rock: 8 ppb

Health Effects of Nitrate

• Methemoglobinemia ("blue baby syndrome") in infants under 6 months
• Increased risk of colorectal and bladder cancer (long-term)
• Thyroid disease from chronic exposure
• Possible reproductive effects

Health risk severity: High. Governed by the National Primary Drinking Water Regulations.

How Nitrate Gets Into Drinking Water

• Agricultural fertilizer runoff
• Animal feedlot operations and manure
• Septic system leachate
• Urban stormwater and wastewater discharge

What to Do About Nitrate in Castle Rock Water

1. Reverse osmosis is the most effective method for nitrate removal
2. Ion exchange systems designed for nitrate can also work
3. Standard carbon filters do NOT remove nitrate
4. Boiling water increases nitrate concentration — never boil for nitrate

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

Related

• Nitrate — National Overview
• Colorado Water Quality
• Castle Rock Water Quality
• Check Your ZIP Code