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quick guide to septic tanks and well water

Quick Guide: Protecting Well Water Through Proper Septic Tank Care


One-third of people in the United States use a septic system to manage their waste. How a septic tank works and how it might interact with the quality and safety of your drinking water are common questions. 

In this quick guide to protecting your well water from septic tank issues, we’ll tackle questions about proper system upkeep and water testing so you can keep everything running smoothly.

Table of Contents:

How Does a Septic System Work?

Septic systems collect, transfer, and treat household liquid wastes before they leak into and contaminate local ground and surface waters, like wells, aquifers, lakes, and streams. Septic tanks are the collection units where wastes decompose and divide into liquids and solids.

how do septic tanks work?
  • Waste is funneled through your household plumbing into your septic tank
  • Solids in the wastewater either dissolve or settle as sludge
  • Grease, scum, and sludge are separated from other waste material
  • Resulting wastewater is sent into distribution section of the tank
  • Purified wastewater is released through the output baffle into a drain field where it filters into the surrounding earth and fertilizes the soil

How Do Septic Systems Fail?

There are a number of ways septic tanks can fail, which can result in the contamination of local water sources. These include:

  • System failure due to clogging
    Proper care is needed to avoid clogging and early-stage system failure. Poor maintenance practices such as disposing of oil, fats, and other inappropriate items down the drain can lead to clogging of the septic system. 
  • Insufficient permeability of surrounding soil
    Sometimes, your local soil is not particularly suitable for a septic system and will not allow passage of the liquid waste released into the leach field. This is an issue that is usually out of the hands of the homeowner.

  • High density of septic systems can lead to problems down the line
    Even if septic systems are placed correctly in relation to wells, a particularly high density of septic systems in one area can be problematic. Waste from many septic systems can combine, which can present an increased hazard to water sources nearby.

How Do You Know If Your Septic Tank Is Full? 

There are a number of easy-to-spot signs that your septic tank is full:

    • Water and/or waste drains slowly (in sinks, toilets, and showers/tubs)
    • Gurgling sounds from your piping
    • Frequent toilet and/or sink backups
    • Unpleasant, sewage-like odors
    • Water has begun to pool in your yard
    • Sudden growth of lush, green grass in your yard

Even if septic systems are placed correctly in relation to wells, a particularly high density of septic tanks within suburban areas can prove problematic. Waste concentrations from one septic tank can combine with concentrations from other tanks, resulting in an aggregated waste concentration that can prove hazardous to surface and groundwater.

What Risks Do Septic Systems Pose to Drinking Water?

While not all septic system failures result in contaminated drinking water, sewage that hasn’t been properly treated by a septic system can cause disease that can impact both humans and other animals. These include:

  • Dysentery
  • Hepatitis
  • Typhoid fever
  • Acute gastrointestinal illnesses

Ignoring the risks can cause serious health hazards for your household.

How to Prevent Septic Systems from Clogging and Contaminating Well Water Supplies 

As a homeowner, you can make adjustments to your system to prevent possible clogging, which helps reduce the risk of contaminating your well’s drinking water supply.

  1. Schedule routine septic inspections and pumping. We recommend that you have your septic system inspected and pumped once every three to four years. Without regular or proper pumping, blockages may occur even if you’re using your system properly.

    Septic inspections and pumping should only be performed by a certified inspector. Candidates include both local health department officials and private contractors. If you do not have a private contractor in mind, you may contact your health department for assistance.

  2. Don’t let the wrong products go down the drain. Some waste items simply aren’t meant to go into your septic system. All of these can lead to clogs or water contamination if clogs lead to system failure: 

    • Fats, greases, cooking oils
    • Motor oils or fuels
    • Coffee grounds, egg and nut shells
    • Cleaners, bleach, paints, or chemicals
    • Prescription medicines, feminine hygiene products or prophylactics
    • Cigarette filters, paper towels, or rags

  3. Observe the warning signs. This one may seem obvious, but it is easily overlooked. Listen for any odd gurgling sounds near your drains, pay attention to uncommon, foul odors, and check your lawn for any slow drainage or wet spots. These wet spots may be the first evidence of sewage leaking to the surface.

  4. Test your water. Having issues with your septic system? A water test might reveal a slew of contaminants that could indicate septic system issues. Our comprehensive home water test kits detect over 100 contaminants, providing you with a detailed water report from an accredited laboratory.

How To Test Your Well Water in a Lab

How Far Does a Well Need to Be From A Septic Tank?

A well should be at least 50 feet away from a septic tank or holding tank.[2] Additionally, it’s recommended that release/drainage fields be located no less than 100 feet from wells.

What to Test Your Water for if Your Well Is Near a Septic System

Some common contaminants may indicate your well is being contaminated by a nearby septic system. These include:

  • Coliform bacteria like E. coli 
  • Phosphates
  • Nitrogen containing compounds like ammonia, nitrate, and nitrite

We have designed a mail-to-lab test kit that covers all these contaminants and many more so you can be sure your septic system is not affecting the quality of your drinking water.

What’s the Takeaway?

  • Issues with your septic system can lead to the contamination of both your own well water, and your community’s groundwater source
  • Proper upkeep of your septic system—which prevents system clogging and backed up septic tanks—helps preserve the quality of your home’s drinking water.
  • Septic system failure can be attributed to factors that you can control (like maintenance) and those that you cannot (like issues with the surrounding soil)

Sources and References

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About The Author


Kate leads operational strategy as COO at Tap Score and SimpleLab. She oversees daily, as well as long-term logistics for tens of thousands of environmental samples across hundreds of certified laboratories. However, she started her environmental testing career by way of scientific blog writing at Tap Score and it continues to be one of her favorite aspects of the business. Outside of Tap Score, Kate loves making homemade pasta, floral arranging, and singing along to Dolly Parton tunes.
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