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Septic System Basics

Septic System Basics
A septic system includes multiple elements, including the tank,
Found that perfect piece of property for building your dream home or getaway cabin? Congratulations! You’re probably not thinking about sewage treatment and disposal, right? But, if your property is not serviced by a municipal sewer system, you’ll need an onsite sewage system (OSS) a.k.a. a septic system. Septic systems are designed to treat—and dispose of—household wastewater. Here’s what you need to know about septic systems.

Gravity Septic System
A gravity septic system is the simplest (and most common) option. This includes a septic tank, drainfield (also known as a leach field), pipes and the soil itself (soil microbes remove and digest contaminants before the wastewater reaches groundwater). These systems should be inspected by a professional at least every three years and pumped when recommended (every three to five years), according to the Homeowner’s Guide to Septic Systems by the Environmental Protection Agency (EPA).
Septic Tank. A septic tank is a buried, watertight tank that holds household wastewater long enough to allow solids to settle out (forming sludge), oil and grease to float to the surface (as scum), and partial decomposition of solid materials, according to the EPA guide. “The septic tank is an overflow device; it should always be full,” says Tom Weaver, septic system designer and partner at Seabeck, Washington-based Allied Design. “When a gallon of wastewater is introduced into the septic tank, it overflows and a gallon of effluent, which has been in the tank for some time and begun to rot, leaves the tank.” Typical septic tanks are made of concrete, fiberglass or polyethylene and have a 1,000- to 1,500-gallon capacity, and newer tanks feature ground surface lids to make tank location, pumping and inspection easier, according to the Homeowners Guide to Onsite Sewage Systems by the Kitsap Public Health District in Bremerton, Washington, which is also the source of the illustration below, and the photo at the top of the post.

Partially treated wastewater flows from the septic tank into the drainfield, which completes the treatment process. The drainfield is a series of trenches that are level to themselves on the bottom and parallel to the contours of the land, and gravity causes the effluent to spread across the entire area of each trench bottom, exposing the effluent to a large area for the liquid to soak into the ground, Weaver says. “The drainfield needs to kill all human pathogens and rot away all organics,” he explains. “If organics do not rot as fast as they accumulate, the drainfield plugs up and eventually fails, causing effluent to surface in the yard or back up into the house.” Gravity septic systems work best in areas with unsaturated and uncompacted soils. If the drainfield is above the septic tank, a pump tank might be added to convey effluent from the septic tank to the drainfield.

Drainfield Size/Type
The size and type of your drainfield is determined by the type of soil in your yard and the daily volume of water used in your house, Weaver says. In Washington State, soils are rated by gallons per day per square foot and vary from .2 gallons per day per square foot to 1 gallon per day per square foot. Here, septic systems are designed to handle a volume of 120 or 150 gallons (this varies by county) per day per bedroom. This is based on EPA estimates that a typical person uses 45 gallons of water per day, assuming two people per bedroom, with an additional 30 gallons per day as a safety factor. In Washington State, the number of bathrooms is not taken into consideration, and all drainfields are designed for a minimum two-bedroom home, even if you are only building a one-bedroom cabin.

Site Constraints and Setbacks
Some septic systems are necessarily more complex (and expensive!) due to the specific site constraints and setbacks of the property. Some of these constraints include:

1. Soil type.
The most common problem is tight, poorly draining soils. “Soils that are mostly silts and clays do not receive liquid as readily as sands and sand loams,” Weaver says.

2. Soil depth.
The depth of soil that is permeable and through which liquid can percolate down can limit the use of gravity systems.

3. Setbacks.
Setbacks impact where you can put your septic system. In Kitsap County, Washington, a drainfield must be located at least 100 feet away from surface water, such as lakes or streams. Other setbacks include wells (100 feet); water lines (10 feet); property lines (5 feet); house foundations (10 feet); and cuts or banks that down slope from a drainfield (25 to 50 feet depending on soil depths).

If your property has constraints, you may end up being required to put in a more complex pressure distribution system or an alternative OSS such as a sand-based media treatment system, an aerobic treatment system, a drip irrigation system or other more advanced technologies.

Design Approval
The septic system design approval process varies around the country. For example, Washington State is a prescriptive state with a universal site plan that homeowners are required to meet in order to get septic system design approval from the health department, which is mandatory before you can get a building permit. Here, the first step is to hire a septic system designer. The designer surveys your site; ascertains existing constraints or setbacks; selects possible drainfield locations; samples, analyzes and describes the soil for the health department; flags and labels soil samples for inspection; draws the site to scale, showing the planned septic system and structures; and submits the design to the health department for inspection and approval. The health department makes sure that your system meets the requirements of the universal site plan.

According to Eric Evans, RS, manager of the Kitsap County, Washington, Drinking Water and Onsite Sewage Program, many U.S. coastal areas, such as California, the Chesapeake Bay, Florida, the Gulf Coast, Oregon and Virginia have restrictive regulations regarding septic systems to protect local waters. Jerry Franklin, supervisor of the Loudoun County, Virginia Health Department, agrees. “We prefer landscape that sheds surface water, not at the foot of a higher slope, with plenty of distance from surface water, and with deep, well drained soil containing no restrictions,” Franklin says. “However, you can’t always get the site and soil that you want and have to work with what you have.” Moving inward toward the center of the country, there are lower population densities and less restrictive soils and regulations, Evans says.

Installing a septic system doesn’t have to be a big deal. Just learn the basics and work with experts.

10 Tips for a Worry-Free Septic System
If you’re building a new home and installing a septic system, here’s how to protect your investment.

1. Hire a professional
. “Don’t buy a piece of property without having a consultation with a septic system designer to find out if it’s developable,” Evans says.
2. Get pre-approval when appropriate. If your property has constraints or your designer has concerns, Evans suggests getting your septic system design approved by the county before you buy the property, even though that means paying for design and approval fees.
3. Communicate with the designer about your new home and lifestyle. Share relevant information such as the number of bedrooms and bathrooms in your home, how many people will live there, whether you plan to add an in-law unit or guest cottage in the future, and whether your household includes teenagers who take long showers or a chef who wants a garbage disposal.
4. Buy quality components. Select the best materials for your system, including sturdy, watertight tanks, pump chambers and distribution boxes. And choose treatment units that have low lifetime costs, can be maintained, provide excellent and dependable treatment, and are manufactured by stable, dependable companies with good customer service. A failing septic system not only smells horrible, but it’s very expensive to fix.
5. Choose your installer carefully. Make sure that your septic system installer is licensed, experienced, a craftsman, and comes with recommendations from satisfied clients. Also, be certain that your installer understands the design of your septic system. A preconstruction meeting between the designer and installer may be necessary. And finally, have at least one complete, detailed inspection of the system by the designer and/or regulator.
6. Location. Locate your tank where a professional can easily access and pump it and can also wash the filters using a nearby water source. Also, make sure that your tank is far enough away from your bedroom that you don’t hear fan motors blowing or smell unpleasant odors.
7. Landscaping.
When choosing landscaping to cover the view of unsightly tank lids, make sure that it doesn’t block tank access or damage the system through root infiltration. Ask you’re your septic system designer or a local gardening expert for advice.

8. Be legal and responsible.
it is illegal to install or repair septic systems without a permit where required and doing so can affect the resale value of your house. 
As a homeowner, you are responsible for maintaining your septic system. “Always remember that contaminants that go down your onsite sewage system that are not treated eventually end up in your drinking water glass,” Franklin says. Don’t overload your system beyond its design limits such as by having eight people use a system designed for six or allowing teenagers to take too many long showers.
9. Alternative septic systems. If you own an alternative system, develop a relationship with a quality operator who does annual inspections of your system and knows how to maintain it.
10. Your septic systems is not a garbage can. Don’t dispose of household hazardous wastes or medications down your sinks or toilets. Also, it’s not a good idea to put a garbage disposal on your septic system because, unlike human waste, undigested food requires large amounts of oxygen to rot (FYI—bulimia can cause septic system failure). Instead of a garbage disposal, consider buying composting bins for kitchen food scraps and putting the compost in your garden. Your plants will love it!. A word about chemotherapy: Unfortunately, it’s a common cause of septic system failure. The same drugs that kill cancer in humans pass through the human body and kill the biological activity in your septic system. Consult a septic system professional in this case.

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