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Think at the Sink – Maintaining Your Onsite Sewage Disposal System

December 25, 2019


goes when you’re done taking a shower or using the bathroom?
If your property is connected to public sewer, then
it goes to a sewage treatment plant before being discharged to
a body of water. But for people who do not have access to public
sewer, the answer is a private onsite sewage disposal system,
also known as a septic system. In Fairfax County, there are
more than 22,000 parcels with private onsite sewage systems.
It’s important that homeowners served by a septic system
Think at the Sink. By understanding how these systems
work and what to do to keep them running properly, you’ll be
maintaining your property values, protecting the
environment and keeping you and your neighbors healthy.
Traditional, or conventional, onsite sewage systems consist of
a treatment unit such as a septic tank and a dispersal area
or drain field. For home sites that have space limitations or
more challenging soil conditions, an alternative
system may be necessary. These systems consist of an
alternative treatment unit, and a soil absorption area or other
method of dispersal. Let’s look at the components of a
conventional onsite sewage system more closely. Here we see
a new single-family dwelling under construction That
four-inch pipe coming out from the house foundation is the
sewer line. It carries the wastewater from its point of
use a sink, a bathtub, a toilet to the septic tank. The
septic tank itself is located underground, outside of the
home. This tank is pretty large and, depending on the number of
bedrooms in the home, could hold as much as 2,700 gallons of
wastewater. The septic tank is sized in such a fashion to hold
the peak amount of wastewater generated in one day for 24-48
hours. The wastewater used in one day is slowly anaerobically
digested and pushed across the tank over that time frame. The
resulting raw or partially treated sewage then goes out to
the dispersal area or is stored temporarily until it gets pumped
to the dispersal area, where it is absorbed in the soil. Now
let’s look at the dispersal area. The dispersal area is an
area that has been designed to accommodate the peak daily flow
of wastewater for that dwelling or building, as determined by
Soil Evaluators, Professional or Certified Soil Scientists, or
Professional Engineers. The dispersal area could be
conventional trenches, a pad, low pressure distribution, drip,
or even an above grade mound. Ultimately the size of the
dispersal area will depend on how many bedrooms in the house
or dwelling, or how much wastewater a commercial building
can generate. Some systems require a pump station to pump
the wastewater to the dispersal area. This is done for one of
two reasons: the first is to overcome gravity; it is
difficult to make water flow up hill on its own; the next is to
control how much sewage goes out to the dispersal area. Now that
you know how onsite sewage systems work, it’s important
to understand how best to maintain them. Proper
maintenance can help extend the life of these systems beyond the
typical 20 years. First, you’ll need to pump your
septic tank or treatment unit out at a minimum of once every
five years. Be sure to notify the Health Department each time
the tank is pumped. Second, if you have a flow diversion valve,
as many septic systems in Fairfax County do, you’ll also
need to turn that valve annually. If you have an
alternative onsite sewage system, you’ll have additional
maintenance to do. At a minimum you’ll need to have the system
inspected annually and have testing done every five years.
You’ll also want to refer to the Operations and Maintenance
Manual that was provided when the system was approved for
additional maintenance steps. Whether you have a traditional
or alternative system, you’ll Don’t overload the septic
system with too much water by using high-efficiency
toilets, spacing the laundry out over the week, and minimizing
the use of garbage disposals. Don’t put harsh chemicals such
as bleach, fats, oils or grease down the sink. Don’t plant
trees on top of or within 10 feet of the septic tank or drain
field. Don’t drive over your septic tank or pump chamber. And
keep good maintenance records. When you have any repairs or
maintenance done to your system, be sure that you use a licensed
contractor. Contractors can be verified by contacting the
Health Department. So next time you flush the toilet or empty
the bathtub, remember that what goes down the drain affects how
well your septic system works. Think at the Sink!

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