How to Read Water Test Results: Understanding Your Lab Report

Understanding Common Water Test Parameters

Water test reports can be overwhelming with dozens of measurements, abbreviations, and numbers. Here's what the most important parameters mean for private well owners:

Bacteria Tests

Total Coliform: This test detects a group of bacteria commonly found in soil and intestines. A positive result doesn't necessarily mean harmful bacteria are present, but it indicates your well may be vulnerable to contamination. Results are reported as "Absent/Present" or as a count (CFU/100mL).

E. coli: This is a specific type of coliform that only comes from fecal matter. Any detection of E. coli means your water is contaminated with human or animal waste and is unsafe to drink. This requires immediate action.

Nitrates and Nitrites

Nitrate (NO3): Often from fertilizers, septic systems, or animal waste. The EPA limit is 10 mg/L (also written as 10 ppm). High nitrates are especially dangerous for infants under 6 months, causing "blue baby syndrome."

Nitrite (NO2): Similar sources as nitrate, with an EPA limit of 1 mg/L. Often tested together with nitrate.

pH Level

The pH scale runs from 0-14, with 7 being neutral. The EPA recommends drinking water between 6.5-8.5. Low pH (acidic) water can corrode pipes and leach metals; high pH (alkaline) water may taste bitter and cause scale buildup.

Hardness

Measured in mg/L or grains per gallon (gpg), hardness indicates dissolved calcium and magnesium. It's not a health concern but affects soap performance and causes scale. Under 60 mg/L is soft; over 180 mg/L is very hard. San Diego County wells often have moderate to high hardness.

Iron and Manganese

Iron: Causes reddish-brown staining of fixtures and laundry. EPA aesthetic limit is 0.3 mg/L. Not a health risk at typical levels but a nuisance.

Manganese: Causes black or brown staining. Health-based limit is 0.3 mg/L; aesthetic limit is 0.05 mg/L.

Arsenic

A naturally occurring element in some groundwater, especially in Southern California. The EPA limit is 10 μg/L (micrograms per liter, also written as 0.010 mg/L). Long-term exposure to arsenic above this level increases cancer risk.

Safe Levels and EPA Standards

The EPA sets two types of standards for drinking water contaminants:

Maximum Contaminant Levels (MCLs): Legally enforceable limits for public water systems. While private wells aren't regulated, these limits represent the best guidance for safe drinking water.

Secondary Maximum Contaminant Levels (SMCLs): Non-enforceable guidelines for aesthetic issues like taste, odor, and staining. Water exceeding SMCLs is usually safe to drink but may be unpleasant.

Quick Reference Table

Red Flags That Require Action

Some test results demand immediate attention. Don't drink the water until these issues are resolved:

Take Action Soon If:

• Total coliform positive (without E. coli): Shock chlorinate the well and retest
• Nitrates between 5-10 mg/L: Monitor quarterly; consider sources of contamination
• pH below 6.5: Corrosive water may leach lead from pipes; consider treatment
• Hardness over 180 mg/L: Consider a water softener for appliance protection

Aesthetic Issues (Not Health Concerns):

• High iron or manganese (staining)
• High total dissolved solids/TDS (taste)
• Sulfur/hydrogen sulfide (rotten egg smell)

Next Steps Based on Your Results

Once you understand your results, here's how to proceed:

If Everything Passes

Congratulations—your water is safe. File the report for your records and test again in 12 months. Consider testing more frequently if you notice changes in taste, odor, or appearance.

If Bacteria Is Present

For coliform without E. coli, shock chlorinate your well and retest in 1-2 weeks. If bacteria returns, you may have a well casing problem that needs professional inspection. For E. coli, use bottled water immediately, shock chlorinate, and investigate the contamination source.

If Nitrates Are High

Identify potential sources: septic systems, fertilizers, animal waste. Consider testing neighboring wells. Treatment options include reverse osmosis (point-of-use) or ion exchange systems. Do not boil water—this concentrates nitrates.

If Arsenic Is Elevated

Arsenic is a natural contaminant in some Southern California aquifers. Treatment options include reverse osmosis, distillation, or specialized arsenic removal systems. Consult a water treatment professional for whole-house solutions.

When to Call a Professional

Consider professional consultation if:

• You don't understand your results
• Multiple parameters are out of range
• Bacteria keeps returning after treatment
• You need help selecting water treatment equipment
• Results suggest a problem with the well itself