Nitrate in groundwater
Frequently Asked Questions

• What is nitrate?
• Where does nitrate come from?
• How does nitrate get into my well water?
• What are the health effects of consuming nitrate?
• How do I know if my water is high in nitrate?
• Where can we have our water tested?
• What do the results of my water test mean?
• What can I do if my water is high in nitrate?
• How often should I test my water?
• How can I guard against nitrate in my water?
• For more information

What is nitrate?
Nitrate is a naturally occurring compound that is formed in the soil when nitrogen and oxygen combine. Small amounts of nitrate are normal, but excess amounts can pollute supplies of groundwater.

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Where does nitrate come from?
Common sources of nitrogen in the soil are fertilizers, livestock waste, and septic systems. Excess nitrate in the soil is most often found in rural and agricultural areas. Some areas of the Llagas Groundwater Basin in southern Santa Clara County have higher than normal concentrations of nitrate.

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How does nitrate get into my well water?
Nitrate travels easily through the soil, carried by rain or irrigation water into groundwater supplies. Wells that tap groundwater may be affected. Shallow wells, wells in sandy soil, or wells that are improperly constructed or maintained are more likely to have nitrate contamination.

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What are the health effects of consuming nitrate?
For most people, consuming small amounts of nitrate is not harmful. Nitrate can cause health problems for infants, especially those six months of age and younger. Nitrate interferes with their blood's ability to transport oxygen. This causes an oxygen deficiency, which results in a dangerous condition called methemoglobinemia, or "blue baby syndrome." The most common symptom of nitrate poisoning is bluish skin coloring, especially around the eyes and mouth. Infants six months of age and younger and pregnant and nursing women should avoid consumption of water high in nitrate.

The good news is that methemoglobinemia is easy for doctors to treat and babies can make a full recovery. Also, as babies grow, their bodies develop the ability to counteract the effects of excess nitrate. Thus, health risks are reduced for children older than six months of age and adults. For more information on the risks of nitrate consumption, consult your doctor.

Cattle, horses, sheep, baby pigs, and baby chickens are also susceptible to nitrate poisoning. They too can fully recover if treated by a veterinarian in time.

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How do I know if my water is high in nitrate?
Nitrate is colorless and odorless. The surest way to tell if you have nitrate in your water is to have it tested. If your water comes from a public water supply, such as a city supplier, it is tested regularly to ensure that it meets safe drinking water standards. If your water comes from a private well, you are responsible for testing it and ensuring that it is safe to drink.

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Where can we have our water tested?
Residents of the Llagas Groundwater Basin area of southern Santa Clara County may be able to have their water tested for free by the Santa Clara Valley Water District. Call the groundwater protection hotline listed below to receive information on the nitrate testing program. For a comprehensive analysis of your drinking water, contact the company that provides your water bill or consult a state certified laboratory. The water district maintains a list of state certified laboratories.

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What do the results of my water test mean?
These guidelines will help you interpret the results of your water test. Be careful when interpreting different lab results. Nitrate can be measured as NO3 or as NO3-N, and the results mean very different things.

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What can I do if my water is high in nitrate?
If the level of nitrate in your water is high, the most important thing to do is to make sure that your family uses an alternative source of water for drinking, cooking and mixing baby formula.

Don't boil the water. Boiling the water before drinking it does not remove nitrate. In fact, it causes some of the water to evaporate, which increases the nitrate concentration.

For a long-term solution, you can treat the water to remove the nitrate. Treatment technologies that remove nitrate include reverse osmosis, anion-exchange, and distillation. Each type of system has advantages and disadvantages, and no single system will correct all water quality problems. Water treatment system vendors are listed in the yellow pages under "Water Filtration & Purification Equipment." Treatment systems are also available at some department stores for the do-it-yourself installers. When you purchase a system, be clear about the type of system that you need, and ask for a guarantee that the system will remove nitrate contamination.

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How often should I test my water?
Unfortunately, nitrate is only one of several possible contaminants in well water. This is why the water district recommends that well users conduct a comprehensive test of their water supply every one to three years, or more frequently if the taste, odor, or appearance of the water changes, or if you have specific health concerns.

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How can I guard against nitrate in my water?
Septic systems, animal waste and fertilizer are all potential sources of nitrate contamination. Water that comes into contact with a source of nitrate can carry that contamination through the soil and into the groundwater supply. Follow these guidelines to reduce the risk of nitrate contamination:

1. Proper well location: Wells should be located uphill (up gradient) and at least 100 feet away from septic tanks, leachfields, animal confinement areas and fertilized areas.

2. Proper well construction: Make sure your well casing extends above the ground, and construct an earth berm around the well to divert surface runoff away from the wellhead. Also, make sure your well has at least a 50 foot deep annular seal (grouting around the outside of the well casing) and an intact concrete slab on the wellhead.

3. Operate your septic system correctly: Maintaining your septic system regularly will help avoid system failure, which can lead to water contamination, the spread of disease, and the need for costly repairs. Follow these guidelines:

• Don't run heavy vehicles over the area above your septic tank, drain pipes or leachfield.
• Avoid planting trees or shrubs near drain pipes or the leachfield. Roots can clog the lines.
• Don't dispose of chemicals or non-biodegradable materials in your toilet or drain.
• Conserve water.
• Install a lint trap on your washing machine.
• Hire a reputable contractor to pump out your septic tank every two to three years.

If you have two leachfields, switch them every year.

4. Reduce your use of fertilizer: Use lawn and garden fertilizers only when necessary, and always according to the manufacturer's instructions. Farmers can use management practices that are both environmentally and economically sound. The Santa Clara Valley Water District will send a free copy of the book "50 Ways Farmers Can Protect Their Groundwater" upon request.

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For more information

To reach water district offices, dial (408) 265-2607. Then enter one of the four digit extentions from the list below:

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