So, I need a Septic System...
Why a septic system?
Septic systems are used when sewage treatment plants are not accessible. They safely treat and dispose of wastewater and protect human health and the environment.
What is a septic system?
The conventional system is one of the most commonly used in North America. It consists of two main parts: The septic tank(s) and the drain fields.
What takes place in a tank?
All of the wastewater from home flows in to a tank (1,000 - 1,500 gal.) first. As the wastewater spends time in the tank, it breaks down, with heavier, solid materials settling to the bottom of the tank, thus forming a sludge layer. Fats, oils and greases float to the top, forming a scum layer. On the outlet end of the tank, a sanitary tee extends approximately 1/3 of the way down into the liquid depth, preventing solids and greases from entering the drain fields. Separation takes place in the tank, with very little treatment. A tank's primary function is to retain the solids and greases, but allow the best water in the tank to reach the drain field.
What happens in a drainfield?
The real treatment of the wastewater occurs in the soil. Wastewater flows out of the septic tank as a cloudy liquid containing many disease-causing germs and environmental pollutants. These enter the absorption field, spread over the bottom of the field and travel down through the soil until they are destroyed.
The soil can also retain certain chemicals, such as phosphorous and nitrogen. Soil varies in makeup and qualities. For example, a heavy, clay soil will not absorb wastewater well, but will treat it well due to its "tightness." Sandy soil is very accepting of water but doesn't treat so well because of its porous structure. A professional from your local health department evaluates the soil and gives the minimum size and maximum depth of the absorption field needed.
What kind of material should I use for my system?
We are fond of saying, a tank is a tank is a tank. Tanks come in a variety of material types: concrete, plastic, fiberglass - even steel. All have their pros and cons, but serve their purpose. Make sure the tank you use is properly teed/baffled on the outlet and the inlet end.
There are a variety of materials used as media for the wastewater to travel through from one end of the absorption fields to the other. The traditional perforated pipe and stone, leaching chambers, graveless pipe (8" perforated pipe wrapped with a sock), and E.Z. flow pipe (a 4" perforated pipe surrounded by 10" of Styrofoam peanuts) are the most common materials used. All these products work well and have their place. We are often asked the question "what works best?". Remember this: the media material you are using is simply providing a way for wastewater to get from one end of an absorption field to the other. The soil treats the wastewater. A particular type of material used will not change the structure, quality, and acceptance rate of the soil.
What design do I need for my absorption field?
We see two basic designs used locally, approved by the board of health. the first one is called an equal flow system.
We affectionately dub the equal flow box an "unequal" flow box. Sometimes this box is called a distribution box, which would be a more accurate term. The theory behind the design is: wastewater flows from the tank into a junction box and the box "equally" distributes it by gravity to different field lines of the absorption field.
Let us think "equal" for a bit. It's a very general term. Soil absorption varies even within field lines that are equal in length. There is also a real possibility of an unseen restrictive layer of rock or unsuitable soil located under parts of the field that could limit a field line's acceptance of wastewater. Fieldlines of the absorption field may vary in inches by width and feet by length.
It's extremely difficult to direct equal amounts of wastewater into each field line even with speed levelers and the ever-evolving attempts to stop the shifting by putting sand, gravel, concrete, etc. around and under the box. If the box is off level even 1/16th of an inch, one line will likely receive all the wastewater due to wastewater just trickling into the box from the tank. Another phenomena is when the soil is dry it shrinks and when it is wet it expands, ensuring a shifting box. While we accept the fact that even house foundations have cracks in them that come and go a distribution box is even more so. The poorer the quality of the soil, the greater the degree of soil shrinking and swelling. Also, the normal black algae-like substance present in the box can build up and restrict wastewater from going into all lines equally even if the box is level.
Now, if any of the field lines are at a lower plane than the "unequal" flow box, the untreated wastewater finds it easier to surface in your yard than to back up the slope to the box and feed other field lines.
We have documented hundreds of the modern, recently installed, failing systems. We observe with interest the Health Department and Installers' response to dodging the very real design problem. Well-meaning environmentalists say:
1."We need to get a good soil cap on this system."
2. "Let's put in an equal flow box with more outlet holes then are needed, in case "we" need need to add field lines in the future."
3. "I want leaching chambers on this site! They have more storage than other media." (soil surface area, not "storage", is equated into any absorption field design)
A sad fact is, the Health Department will design, permit, inspect, and "approve" (meaning they will not assume responsibility for the system if it fails) this fragile design on less than desirable sites.
The second sad observation is to see homeowners try to fix the problem. It's akin to putting a band-aid on an infected appendix. They rarely get the Health Department involved again, so..
1. They dig up the box and re-level it, only to have it re-surface at a different line.
2. Separate the washer drain from the system and run contaminated water over the hill.
3. Finally convince an installer to add another 100' of field line only to have a different fieldline surface.
4. Buy loads of expensive top-top to cover the offending line on to have it pop out the hillside later
5. Tie the ends of the field lines together and run them into a road ditch.
It's hard to fix the problem long-term, outside of converting the system over to a "Hillside" system, which is our second option.
In our opinion, based on observation since 1988, an equal flow box should never be used unless all fingers of the absorption field are on the same plane.
If your environmentalist or installer insists on installing this "prone to fail equal flow design" on a site other than level, ask them to be responsible for any surfacing issues for the next twenty years.
Our second basic design is one we highly recommend for several reasons.
1. It is not designed with "equal" as a premise. Fieldlines don't have to be equal in length, making them easier to fit on small and cluttered site.
2. It is easier, and quicker to install than an equal flow system.
3. Less material is used with a hillside system making for a cost effective system and also making for less drain on our resources.
4. Best of all, you will never have wastewater surfacing. We don't know of any "weak" issues with the hillside design.
The box set at the beginning of every ditch (except the final ditch) works on the same principle as a spillway on a body of water. When the liquid level rises to the top of the field line media, it can spill over to the next line.
Some believe that the first line must fail before the second line receives any wastewater. Not true. Cap off a line that is completely full and watch it dry up in two weeks time. When a line becomes full, there is simply more wastewater going into it than it can accept, so it spills over to the next field line instead of surfacing in your yard.
If wastewater ever surfaces from your lowest field line, you will have exceeded your entire system's maximum capacity, not only one line as in the "equal" flow design. A hillside system does not surface because it is not poorly designed. We have seen hillside systems that have worked flawlessly for 40-45 years.
The hillside system is the most economical and dependable system we have observed since 1988. Insist on and install a hillside system design for peace of mind.