San Marcos, California

What is the Water Quality in San Marcos, California?

[Updated: June 9, 2023]

Compared to other US cities, San Marcos water quality ranks in the high range for contamination excluding Lead.

Most of their 33 contaminants have cancer-causing attributes.

• Arsenic is at extremely high levels: 700x health guidelines.
• Haloacetic acids (HAA5) are at extremely high levels: 83x health guidelines.
• Haloacetic acids (HAA9) are at extremely high levels: 171x health guidelines.
  • These are both byproducts of the chlorine treatment process most water supplies go through.
• Uranium is at high levels: 4.6x health guidelines.

Let’s look closer at what’s in San Marcos water.

What’s in San Marcos water?

Here are the top 6 chemical compounds in your water and what health issues they can potentially cause:

1. Arsenic – Potential effect: Cancer
2. Bromodichloromethane – Potential effect: Cancer
3. Chloroform – Potential effect: Cancer
4. Haloacetic acids – Potential effect: Cancer
5. Hexavalent Chromium – Potential effect: Cancer
6. Total trihalomethanes – Potential effect: Cancer

These are six of the 33 contaminants analyzed by the Environmental Working Group (ewg.org).

15 of these contaminants are rated as exceeding EWG Health Guidelines.

Does San Marcos water have Lead contamination?

Yes, the most recent Lead samples collected from 2017 through 2019 showed concentrations of 1.1 parts per billion (ppb).

The legal limit for lead is 15 parts per billion. Being well-below this level is a good thing.

• Concentrations between 3.8 ppb and 15 ppb put a formula-fed baby at risk of elevated blood lead levels. Read more about the symptoms of Lead in water.

There is no safe level of lead for humans.

• The good news is that 99.99% of the lead can be removed.

See the What Can You Do? section below to learn how to filter out contaminants.

Where does San Marcos’s water come from?

San Marcos’s water comes from the San Marcos Creek watershed.

All 10 EPA assessed water sources in the San Marcos Creek watershed are in Impaired or Unknown condition. These include:

• Batiquitos Lagoon
• Encinitas Creek
• Lake San Marcos – 3 segments
• San Marcos Creek – 4 segments

Ideally, a water source would be rated in Good condition.

Whether a water source is in Impaired or Good condition refers to the quality of these uses:

1. Drinking Water
2. Aquatic Life
3. Fish and Shellfish Consumption
4. Recreation

Learn more from How’s My Waterway

See below for what you can do to improve San Marcos’s water.

Conclusion – What Can You Do?

Information about San Marcos water quality can be surprising.

But there are things you can do in your home to clean up your water.

1. Test Your Water using Varify Home Test Kits or similar.
2. To Remove Lead and Other Contaminants In Your Home:

• Use Activated Carbon filters to remove most contaminants in your drinking water.
  • Faucet-mount filters work better than pitchers.
  • PUR and Brita are low-cost and effective.

• To filter out even more contaminants, consider a Reverse Osmosis water filtration system for your house.
  • These are more expensive than pitchers to purchase, but can be more effective.
  • They have the benefit of filtering out heavy hitters like:
    • Arsenic – health risks
    • Barium – health risks in water
    • Bromate
    • Bromochloroacetic acid
    • Bromodichloromethane – health risks in drinking water
    • Bromoform
    • Chloroform – side effects
    • Dibromoacetic acid
    • Dibromochloromethane
    • Dichloroacetic acid
    • Dichloromethane
    • Fluoride
    • Haloacetic acids – chlorination byproduct*
    • Hexavalent chromium – health effects
    • Molybdenum
    • Monobromoacetic acid
    • Monochloroacetic acid
    • Nitrate
    • Nitrite
    • Strontium
    • ter-Butyl alcohol
    • Total trihalomethanes – byproduct of chlorination*
    • Trichloroacetic acid
    • Uranium
  • Our recommendation: APEC Reverse Osmosis Systems

*Chlorination is an effective method of disinfecting/treating drinking water. You can then use a water filter to reduce the effects of chlorination byproducts to get the safest, cleanest water possible.

In Your Community:

Contact your local government officials and put pressure on them to invest in cleaner waterways and upgraded city water filtration and treatment.

Go to: https://www.san-marcos.net/your-government to find contact information for your local officials.

Water Quality in Other California Cities

California Water Quality Page