The Basics of Septic

According to the U.S. Environmental Protection Agency (EPA) 25% of Americans rely on septic systems for treating household waste. That really means that a large portion of the non-urban population relies on septic systems; and if you are buying a home you need to understand on a most basic level how these systems work and have a the system inspected by a licensed professional before purchasing a home. According to the EPA the average lifespan of a septic system is 15 to 40 years. Though  it can last longer if properly maintained, these are very expensive systems to replace and the condition of a septic system should be carefully examined before buying a home.

All the information below is from the EPA’s Septic Smartprogram, the Rural Community Assistance Partnership, the Illinois State Water Survey, and Private Well Class.org. and is presented here in an edited form.

Conventional septic systems rely on natural degradation of organic material (human waste, skin, soap, etc.) by bacteria to reduce household wastewater so that it can be allowed to flow into the drainfield and harmlessly infiltrate into the groundwater. The image below appeared in presentations of all the above listed organizations. I believe that the citing on the label is the correct one.

You can see the edge of the house in the left hand corner. The wastewater flows from the toilets, sinks, tubs/showers and drains into the septic tank. Once in the tank, the solids separate from the liquid by gravity and sinks to the bottom. Once on the bottom the bacteria have time to do their job of breaking down the organic waste material. Liquids leave through a pipe near the top of the tank and are transported by pump or gravity to a drainfield where the wastewater is allowed to seep into the ground by perforated piping that makes up the underground portion of the drainfield.

It is important that scum from the top layer in the tank and solids from the bottom of the tank are not carried out to the drainfield where they will clog the holes in the perforated pipes. The solids must stay below the intake to the exit pipe (as shown in the picture) and the scum layer of grease must stay above the intake. If the tank is not pumped frequently enough (or is too small for the household use) the solids and scum get pulled out into the drainfield. 

Septic system regulation is relatively new. Most septic regulation date only from about 25-30 years ago and were strengthened in the past 10-15 years. Thus, many relatively new homes can have problematic septic systems. Properly designed, sized and maintained septic systems can last for decades; however, a system that was adequate for a small home when it was built may be entirely undersized for the home after it has been enlarged or a garbage disposal added, sump pumps or water treatment systems discharging to the septic system, or adding a whirlpool.

The EPA lists the  signs of a septic system malfunction in their “NewHomebuyer’s Guide to Septic Systems.”  The biggest signs that a septic system is failing is:

• Wastewater backing up or gurgling into household drains (especially when a toilet if flushed).
•  A strong odor around the septic tank or drainfield.
•  Bright green, spongy grass appearing on the drainfield.

Don't depend on just your observations when purchasing a home.   The septic system is expensive to repair or replace so you want it to be in good condition when you buy the home. Have the system inspected by a professional, in Virginia that is a DPOR licensed septic professional to inspect the septic system before you purchase a home. Virginia is a buyer beware state. (States like Massachusetts require a Title 5 septic inspection to sell a home.)The inspector should check for the following:

• Pumping and maintenance records;
• The age of the septic system;
• Sludge levels and scum thickness in the tank;
• Signs of leakage, such as low water levels in the tank;
• Signs of backup, such as staining in the tank above the outlet pipe;
• Integrity of the tank, inlet, and outlet pipes;
• The drainfield, for signs of system failure like standing water;
• The distribution box, to make sure drain lines are receiving equal flow; and
• Examine available records from the town or local Health Department, to ensure the system complies with local regulations.

A typical septic system should be inspected every three years by a septic system service provider. The tank should be pumped as recommended by the service provider or as required by your town, county, or state. In Prince William County (and Fairfax and Loudoun) it is required to pump septic tanks at least every 5 years. Alternative septic systems must be inspected every year in Virginia and many states. Here in Virginia the inspection records should be filed with the Health Department along with the record of septic tank pump outs.  

Being careful of what you put down the drain and flush down the toilet (only waste water, and human waste and toilet paper NOT wipes) and pumping your septic tank every couple-three years is the cheapest way to extend the life of you septic system.  Simple maintenance, making sure that excess scum, waste and trash is not thrown into the toilet or down the drain and carried out to clog the perforated pipe will extend the life of your system for a few hundred dollars.