Private Well Water in East County San Diego: What to Test For, and Why Testing Comes First

Who is responsible for testing a private well in San Diego County?

The owner. The State Water Board's guide for well owners states that California does not regulate the water quality in private domestic wells, and San Diego County's sampling guidance says it remains the private well owner's responsibility to maintain the health standards and safety of their water supply. No agency tests your well on a schedule.

The county does require testing at specific moments. Its sampling guidance says that, at a minimum, testing for bacteria and nitrates is required to verify a potable water supply before the county issues a building or septic permit, and that the sample must be taken by a qualified provider, not by the owner or the well driller.

After that, the schedule is up to you. The county stopped providing water sampling services in 2018 and publishes a list of qualified sampling providers that points to California's certified laboratories.

What should you test a private well for, and how often?

The State Water Board recommends testing every year for total coliform bacteria, nitrate and electrical conductivity, and testing general minerals, including iron and manganese, every 5 to 10 years or whenever something changes. The EPA's annual list adds total dissolved solids and pH. Use a lab certified for drinking water testing.

Bacteria and nitrate are the priority tests because they are the health ones. For county permits, a sample is considered potable if no coliform or E. coli bacteria are present and nitrate, measured as nitrogen, is no more than 10 mg/L. The county notes it does not currently allow any nitrate removal system for private water supply wells, which makes knowing your nitrate number especially important.

What do iron and manganese do, and what are the limits?

Iron and manganese are aesthetic constituents in California, meaning their limits are about taste, color and staining rather than health. California's secondary standards are 0.3 mg/L for iron and 0.05 mg/L for manganese. Above those levels, iron tends to leave orange-brown stains and manganese dark brown or black ones.

Those limits come from California's secondary drinking water standards, and the State Water Board's well owner guide uses the same numbers as comparison levels. They are the levels above which people usually notice the water, not thresholds for illness.

Iron and manganese also matter for equipment. The manufacturer warranty on the softener we install does not cover resin and internal valve parts on systems used to remove iron, manganese or chlorine above the suggested level. That is one more reason the test comes before the purchase.

What has the state found in San Diego County wells?

The State Water Board's GAMA program sampled about 137 domestic wells in San Diego County in 2008 and 2009. It reported manganese above the secondary standard in 45 of them, about 33%, and gross alpha activity above recommended levels in 35% of the 54 wells tested for radionuclides. That describes a sample of wells, not yours.

The GAMA Domestic Well Project is the best regional snapshot available, and the GAMA Groundwater Information System lets you look at sampled wells on a map. Both are useful for knowing what to ask your lab about. Neither can tell you what is in a specific well, because groundwater changes from one property to the next.

We are not going to guess what is in your well, and you should be wary of anyone who does, especially anyone selling equipment. The honest answer to what is in my well water is: whatever the lab report says.

How do you get a well tested?

Use a laboratory certified by California's Environmental Laboratory Accreditation Program for drinking water. Many labs provide bottles and instructions, and some send someone to collect the sample. For a county permit, the sample has to be collected by a qualified provider. Ask the lab which tests fit the state's recommendations.

San Diego County's DEHQ publishes a water sampling provider list and a water wells page with its duty desk contact. The State Water Board's GAMA program links to its well owner guide, which walks through testing in plain language.

Collect the sample the way the lab tells you to. Bacteria samples in particular are sensitive to how the tap is cleaned and how quickly the bottle gets back to the lab.

What treatment makes sense for well water?

It depends entirely on the lab results. Bacteria call for disinfection and finding the source. Iron and manganese call for filtration designed for them, usually before any softener. Hardness calls for a softener or conditioner. Sediment calls for a sediment filter. Buying equipment before testing risks paying for the wrong system, or a system the water will damage.

Once you have results, our salt-free vs softener comparison and cost post help with the hardness side. Hardness is often the last step on a well, not the first.