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Environmental Health Services

Septic System Frequently Asked Questions


What is Greywater?

Greywater is the wastewater, excluding toliet waste, that comes from plumbing fixtures in the home.  It includes waste from washing machines, sinks and bathtubs.  Greywater contains bacteria that can make people sick (pathogens) and must be disposed of in an approved sewer or septic system.

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Can I use Greywater to water plants at my home?

Once water enters the drain of a plumbing fixture, it must be connected to an approved wastewater system.  It is illegal to disconnect drains to use the water for irrigation or other purposes.  It is considered by some to be acceptable to capture bathwater or dishwashing water in a pail to use for plant watering.  If this is done, the water must be used immediately and should not sit around for a long period of time before use.

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How often do I need to pump out my septic tank?

For maintenance, a septic tank should be pumped to keep the system working properly. How often it is pumped depends on the amount of sewage generated, the size of the family and the size of the tank.  Generally, a septic tank should be checked every 5 years to see if it needs to be pumped.  NCSU's Septic Systems and Maintenance Web site provides more information.

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When should I have my septic system inspected?

A septic system should be inspected at least every 5 years to check if the septic tank needs pumping and for other operational problems.  A list of certified inspectors is available from the state certification board website.  If you suspect problems with the system including wet areas in that area of your yard, slow draining plumbing or sewage odor, you should contact our office to come out and check out the system. 

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How long should a septic system last?

A conventional septic system has a typical life of between 20 and 40 years.  There are many factors that will affect the useful life including soil type, landscape position, amount of water used in the house and most important – maintenance of the system.

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What do I need to do to maintain my septic system? 

To maintain your septic system, you should conserve water, don’t flush chemicals or grease down the drain, maintain the groundcover over the drainfield, and have the tank checked every 5 years. Our septic system page offers more information on septic system maintenance.

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What permits are needed in order to build a house? 

For homes or businesses built where the sewer system is not available, the following permits will need to be issued by Environmental Health:

1. Improvement Permit: This is a permit that is issued for sites that have acceptable soil to support a septic system.  Some lots that have been recently subdivided already have an issued improvement permit.  Check with our office to get a copy of the improvement permit.

2. Construction Authorization: This is the permit that allows for the installation of the septic system and must be issued before the building permit is issued.  To get a construction authorization, you must submit an application with a floor plan of the building and a site plan of the property.

3. Well Permit: If the property is not served by public water, you will also need to apply for a well permit

Application for permits are available on our Web site.

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What if I have an existing house that I want to replace or add on to? 

If you are not increasing the number of bedrooms and the addition does not encroach on the septic system or well, you will need to apply for an Existing System Authorization.  You will need to submit the application along with a floor plan and site plan.  Our office will visit the site and if there are no problems, will issue the authorization before the building permit can be issued.  If the number of bedrooms is increasing, or the septic system needs to be relocated, you will likely need to apply for an Improvement Permit and Construction Authorization.  Please talk with one of our staff to make this determination.

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How long is my permit good for?  

Improvement Permits and Construction Authorizations are valid for 5 years.  It is possible to get an improvement permit that has no expiration.  For this type of permit, the application must contain a plat prepared by a registered land surveyor to a scale of 1”= 60 feet or less, showing the house location, driveway, water supplies, surface waters and other structures.  Please talk with a staff member if you are interested in this type of permit.

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What is a Perc Test?  

When people say that land percs, they are implying that the land has been evaluated, and a site on the property has been identified as acceptable for a septic tank system. Be cautious of claims that a certain property has been “perked” unless a valid permit has been issued by the Health Department. "Perc" test is an antiquated term that refers to the practice of digging post holes and pouring water in them to see how quickly the water percolates or is absorbed into the ground. This type of testing was replaced in the mid 1970s with a comprehensive soil and site evaluation. An evaluation consists of several auger borings or pits where our staff evaluates the soil texture, structure, consistence, and evidence of long-term drainage performance as indicated by color. If an adequate area of soil is found with suitable soil and topography, our staff will issue an Improvement Permit indicating the site can be used for a septic system drainfield (absorption field). Permits are good for 5 years.

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What is a conventional septic system?  

A conventional septic system refers to the type of  drainfield on a septic system.  After sewage passes through the septic tank, it goes to a drainfield (also known as a leach field or absorption field).  The drainfield consists of a trench filled with gravel and a pipe or some other material that allows the liquid from a septic tank to percolate into the soil.

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What size does a septic system need to be?   

Septic systems are sized according to the number of bedrooms in a house. The more bedrooms, the bigger the tank size and more area required for the drainfield.  If a property has a permit for a 3 bedroom home, and you wish to have a 4 or 5 bedroom home, you will need to apply for a new improvement permit and construction authorization in order to increase the size of the septic system.  It is important to note that for the purpose of sizing septic systems that a bedroom is considered to be any room in the home that can reasonably function as a bedroom, regardless of the current use of the room.  A typical 4-bedroom septic system and repair area will need about 1/4 to 1/3 of an acre of acceptable soil.

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Why do septic systems fail? 

There could be several factors affecting whether a septic system will fail including age, soil conditions, water usage and the level of maintenance.  Many system drainfields fail because of tree roots that grow into the trenches seeking water and nutrients.  Many other systems fail because of leaking plumbing that overloads the septic system drainfield.  All septic systems will eventually reach their capacity to treat and absorb wastewater. For this reason, it is important to know where your repair area is and to make sure that nothing happens to it.

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What is a repair area? 

A repair area is an area of suitable soil that is reserved in case the original drainfield fails.  After the repair field is installed, an owner will be able to switch from the old drainfield to the new drainfield and back again.  While one drainfield is working, the other one is resting and rejuvenated. Alternating the two areas allows for a system with an indefinitely longer life.

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What kind of trees can I plant near the septic system? 

The best ground cover over a drainfield is a well maintained grass cover. While it is not recommended, an owner may choose to plant trees near the drainfield area.  The exact location of the drainlines need to be known so that a tree is not planted on top of the drainline.  Most modern drainfields have only 6 to 12 inches of backfill over them, and the pipe and trench can be damaged by planting trees too close or on top of the drainline.   If trees are planted near the drainfield, you should avoid species that are known to have problem roots.  These species include maples, elms, willows, sweetgum and any tree with fibrous roots. 

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How can I find out where my septic system is? 

Our office has records that show the septic system location for most county properties.  You may request the file information for your property by filling out an online request.

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