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. 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. 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. 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. 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. Farmers can use management practices that are both environmentally and economically sound.