Septic System Design and Maintenance

Save money by getting to know your septic system design and maintenance procedures.

| March/April 2011

  • Septic System Drawing
    This illustration shows the complete septic system, from plumbing vent to septic tank to drain field.
    illustration by Nate Skow
  • Septic System Trench
    Readying PVC pipe to be laid for the septic system. It’s a dirty job, but somebody’s got to do it. Schupp
  • Installation of Septic Tank
    Installation of a septic tank showing diverted pipework. Garbet

  • Septic System Drawing
  • Septic System Trench
  • Installation of Septic Tank

Sometimes, we take things for granted. A hot shower, a load of laundry or a flush of the toilet may be just a routine part of our day, but it can add up to a lot of water down the drain. In fact, the average person uses between 50 and 70 gallons of indoor water each day, and the majority of us don’t give a second thought as to where all that wastewater is headed. Take a little time to understand septic system design, and you're sure to save a bundle of money in the long haul.

More than one-fourth of all homes in America have a septic system, and each one requires maintenance to keep it running properly. With prices for new septic systems ranging from $3,000 to more than $40,000, depending on the type of system and the cost of installation, proper maintenance can mean big savings.

How it works

Since most septic systems are underground and out of sight, they’re easily ignored until things go wrong. Whether you’re installing a brand-new system or you’ve
inherited an older one, becoming familiar with it can save headaches and dollars. Maintenance of a private system is the homeowner’s responsibility. Understanding how it works is the first step in caring for it. Most basic septic systems have three main components:

  • Household wastewater pipe – Each time you turn on a faucet or flush a toilet, wastewater is carried through a pipe and into your septic system. The number of people living in your home and your water usage habits determine the flow going into the system. If a system isn’t designed to handle the volume of wastewater flowing into it, an overload occurs, and that can mean big problems for a homeowner.
  • Septic tank – The size of the tank is determined by house size and water usage. It may also be mandated by state and/or local regulations. The number of bedrooms is a good guide. A three-bedroom house typically requires a 1,000-gallon tank, and it increases 250 gallons for each additional bedroom.
  • Inside the tank, the heavier solid material sinks to the bottom, and fats and grease float on top. The liquid effluent in between flows out to the drain field (or in some older installations, a rock-filled pit called a French drain) through a T-shaped outlet that helps prevent solids from escaping. A screen or filter is required in some states to prevent solids from escaping. The sludge –
    solids that collect in the bottom of the tank – periodically has to be removed by pumping. Some tanks have risers with bolted lids that allow easy access for checking sludge levels without opening the tank.
  • Drain field – An underground pipe carries the liquid effluent from the tank to the drain field, where it’s distributed into a series of shallow trenches lined with gravel and covered with soil, or plastic chambers covered with soil. The soil in the absorption field is loaded with bacteria, which purify the liquid waste before it makes its way into groundwater.
  • The area ideally should be covered with nothing but grass. Tree roots, heavy vehicles or even compaction from excess foot traffic can cause irreparable damage.

Existing systems

Jan Hygnstrom, extension project manager for the University of Nebraska-Lincoln, says some experts believe systems that have been well-designed and maintained can last 30 years or more, but that’s not always the case. Drain fields that have been overloaded, have compacted soil, or that were installed or maintained poorly may have a much shorter life span.

Sometimes it can be difficult to locate the tank and drainage field, especially with older systems that are completely buried. Most county health or building departments keep records showing the exact locations of private septic systems. If you don’t have a drawing of your system, you can try to locate it by finding the wastewater pipe that runs from the house to the tank, usually the largest pipe exiting your house. The tank should be directly in line with the pipe. Use a long metal rod to probe the ground, starting about 10 feet from the house. If you are still unable to locate your system, a professional can help.

Septic experts also can help determine the condition of your system and whether it’s adequate for your home and family. Additions and renovations can cause a home to outgrow its system, since more household members mean an increased wastewater flow. Hygnstrom recommends monitoring wastewater usage over a set period. “Have the tank pumped after a year of use,” she says. “At that point, he (a service person) should be able to recommend a good pumping interval, as long as you have the same water usage.”

6/18/2015 2:47:05 PM

I like your point about the fact that, because septic systems are underground and out of site, they are usually ignored until there is a problem. However, regular maintenance can ensure that the water system doesn't fail when you least expect it. Thank you for covering the three main components of the septic system. Do you have any suggestions as to what needs to be done to maintain each component.

4/16/2015 9:04:58 AM

I didn't realize that a garbage disposal may not be the best for a septic system. I've been considering having a disposal installed, but I may have to rethink that. I've had septic problems in the past. I want to everything I can to avoid anymore.

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