If you’re considering buying a home in Middle Tennessee, it may or may not be connected to a city sewer. 

While most homes in Nashville are on public sewer, many suburban and rural homes in Davidson County and surrounding counties have septic systems instead.  

For such homes, the septic system is an important component of the property you’re buying, since everything you put down the drain in your home will end up in the septic system.  As a homebuyer, it’s therefore important to make sure that the septic system is in good repair and adequate for your family’s needs.  Otherwise, you could have significant unexpected expenses to repair or replace the system after purchase.

What is a Septic System, and How Does it Work?

Septic systems are actually simple on-site wastewater treatment systems.  A septic system is comprised of a septic tank, a soil absorption field or drainage field, and the pipes that connect it all together.  The main soil pipe routes wastewater from the home, including kitchen, bathroom and laundry waste, to the septic tank.  The septic tank is a water-tight tank usually made of concrete, fiberglass or polyethylene, and is buried underground.  Treatment begins as waste is collected in the septic tank, where it separates into three layers.  The solid waste settles to the bottom, forming an organic sludge, and any oils and grease float to the top as scum.  The partially clarified liquid wastewater, also called effluent, is the middle layer, and flows from the tank into the drainfield.  Tanks are designed to prevent the sludge and scum layers from exiting the tank into the drainfield when everything is operating properly.  Bacteria found naturally in the wastewater break down the solid matter remaining in the tank.  The scum and sludge that can’t be broken down are eventually pumped from the tank by a professional septic service, generally every three to five years.  

The middle layer of partially treated wastewater flows to the drainfield (sometimes called a leach field), where perforated pipes or drain tiles are laid in a series of trenches or a bed of gravel and/or coarse sand, buried a few feet below the surface.  This distributes the wastewater and allows it to slowly percolate through porous gravel, sand and soil, which act as biological filters to naturally break down and remove harmful bacteria, viruses and nutrients.  

An overloaded drainfield can flood, allowing sewage to back up into household plumbing, or flushing the tank too rapidly and allowing untreated sewage to flow to the ground surface.  Overuse of water in the house, or routing rainwater drainage too close to the drainfield can overload its absorption capacity. 

Click this link to view an animated, interactive model of how a household septic system works  (created by the Guadalupe-Blanco River Authority.)  https://www.gbra.org/septic/index.html

Septic Systems in Middle Tennessee

Septic systems vary in size and capacity.  Tennessee Code sets requirements for tank size by the number of bedrooms.  In order to obtain septic or building permits, the lot or building site is assessed to determine the feasibility and suitability for onsite sewage disposal systems.  This usually involves one or more types of soil analysis to ensure the soil absorption and drainage is adequate.  Then, the size and type of system permitted is determined based on this analysis and the projected water usage.  While you might think the number of bathrooms should be the determining factor, the best indicator of water use for a single family dwelling is the number of bedrooms.  Thus, typically, residential septic systems are permitted for a maximum number of bedrooms.  It is wise to verify that a property’s septic system is rated to support at least the number of bedrooms advertised or the number desired, especially if you are considering renovations or additions to a home.

Importance of a Septic Inspection When Buying a Home

A standard home inspection is a wise move, but generally does not include a full and detailed inspection of the septic system; this is beyond the scope of a general home inspector’s experience and training.  A general home inspection will usually include a visual inspection of the plumbing.  The inspector will run all the water and flush all the toilets, to look for leaks, check the water pressure, and see that everything is draining appropriately.  The inspector may also visually check the drainfield area, to ensure there is no standing water or apparent sewage leak.  

In Tennessee, businesses with permits to install or pump septic systems typically provide septic system inspection services as well.  These experts have the ability to pump (empty) the tank and gain access for a more comprehensive inspection than a general home inspector can perform.  Full septic inspections for existing systems should include everything above, as well as an evaluation of the drainfield conditions and the condition of the tank.  The tank may need to be pumped to give the inspector visual access to the tank components.  The septic inspector should be able to give you an idea of how well the sellers have maintained the system, based on the current condition.  They should also be able to determine the location and sizing of the drainfield and of the tank, and an indication of whether it is adequate for the number of bedrooms.  

Additional valuable information may come from asking the sellers about any history of problems or repairs, and from an independent records search.  In 2018, the Tennessee Department of Environment and Conservation established a website (https://tdec.tn.gov/filenetsearch) where homeowners, prospective home buyers and others can search for a property’s septic records. Data includes whether a property has a functioning septic system, where it is located, when it was inspected and what was found during the inspections.  Information for some counties, including Davidson County/ Metro Nashville, is not included.  For properties in Metro Nashville, information may be available through the Health Department.  

Final Note

Buying a home is arguably one of the most important investment and lifestyle decisions a person or family makes.  When I have the opportunity to represent homebuyers, I work with them each step of the way to make sure they are thoroughly aware of the due diligence options available to them, inclusive of septic inspections, as applicable.  If you’re considering buying a home in Middle Tennessee, give me a call and let me help you through the process, from start to finish.