SEPTIC SYSTEMS... CARE AND FEEDING
A few months ago, I asked my longtime friend Ralph Stanton... superhero soil scientist, civil engineer, and sanitarian... to give me some information about septic systems from the view of a professional, as opposed to my views, which are those of an end user (pardon the pun). I had received a number of requests from my readers, and, though I always have something to say on any home repair topic, this was one subject of which I had only the most meager knowledge. Well, that has all changed. So if you want to know more than you ever thought you needed to know about septic systems, it's all here.
Keep in mind that the requirements for septic systems vary throughout the world. That which is acceptable in some areas is prohibited in others. So, take this for what it is... a primer to increase your general knowledge of how these systems work, how they fail, and how to protect your investment.
REMEMBER... you can flush anything, including your spouse, your career, or your reputation down the toilet. Just don't complain to me when it comes back to haunt you!
Oh, and thank you, Ralph!!
SPECIAL REPORT written for The Natural Handyman by Ralph H. Stanton, Jr., P. E., R. S., S. S., Canaan, CT. 06018
WHAT IS A SEPTIC SYSTEM?
A Septic system is simply an onsite subsurface sewage disposal system for your home. It takes household sewage wastes and discharges the liquid portion to the ground. Septic systems are a standard method of sewage disposal in rural and suburban areas where centralized sewer treatment plants are not available, not affordable, or not desired. A properly designed and installed septic system with regular cleaning and maintenance of the septic tank can last indefinitely and be the most cost effective and least labor intensive method of sewage disposal.
In its most basic form a gravity Septic System consists of a Septic Tank connected by solid pipe to some type of leaching system.
If you would like to view a diagram of a typical Septic System, click HERE
The septic tank is a large tank of usually 1000 gallon capacity or more. The size is generally based on the number of bedrooms which denote a certain amount of water usage per day. Today the tank is generally constructed of concrete, plastic or fiberglass and is designed to be water tight. Click HERE to view a typical septic tank
The function of the septic tank is basically as a settling tank and/or clarifier. Most of the work done in the tank is settling. Some decomposition goes on with the sludge but it is usually very slow because the temperature is relatively low and due to the general lack of oxygen in the sludge mass, the process becomes mainly anaerobic-septic (methane and hydrogen sulfide compounds are created - rotten egg smell), hence the name Septic Tank.
In action the septic tank can be thought of as a corporate or political organization. The masses enter the tank (liquids and solids) by dropping through the inlet pipe/ baffle. The (lazy) heavier particles sink to the bottom (according to Stoke's Law) and become the sludge, some particles, grease, and gas rises to the top of the liquid as the (leaders-executives) scum. The main body of water circulates through the tank and then flows out the outlet pipe and baffle. This water is normally gray in color because of the fine particles that stay suspended (the silent majority) and are carried out to the leaching system.
The Leaching System
The LEACHING SYSTEM may consist of perforated PVC (plastic) pipe set in clean 1.25 inch diameter stone in trenches a 1 - 4 feet wide and 1.5 feet deep, or some type of gallery structure (a hollow concrete or plastic structure with an open bottom).
After the careful analysis of the soils by an experienced Soil Scientist, Professional Engineer or Registered Sanitarian, the type of leaching system is determined. The leaching system, if conditions allow, will be placed in the upper part of the subsoil known as the Bw horizon. The reason we place the leaching system into the upper part of the subsoil is that this horizon is where there oxygen is plentiful and the biological activity is greatest (excluding the top soil or A horizon).
Unlike the septic tank, the leaching system to be most effective must operate in aerobic conditions (with oxygen present). Therefore the septic effluent leaving the leaching system entering the subsoil will acted upon by the aerobic soil bacteria to “treat” it or remove the pathogenic bacteria and viruses and some of the chemical nutrients. If there is ground water or some restrictive condition (dense glacial till [mixed sand, silt, gravel and clay] or bedrock-ledge) the leaching system must be kept elevated above (according to local health codes) a certain number of feet. This is done to prevent: unwanted partially treated sewage effluent from directly entering the bedrock or directly entering the ground water and possibly contaminating a nearby water supply well.
Also if a restrictive layer is directly beneath the leaching system the leaching system will tend to stay mounded with water in it and after a while it will become anaerobic (once the oxygen has been used up) then the system will fail. When these soil conditions are found the experienced Soil Scientist, Professional Engineer or Registered Sanitarian will often call for the use of a Uniform sand fill to elevate the leaching system (providing the existing subsoil can support or handle the volume of sewage effluent being discharged). That is why many of the new and repair septic systems designed and installed today are in sand mounds.
WHY SEPTIC SYSTEMS FAIL
If the partially treated sewage effluent from the septic tank cannot soak into the soil surrounding the leaching system, sewage may back up in the system and overflow into the house or puddle on the surface of the ground. There are several possible causes of this problem.
1. POOR SOIL CONDITIONS
A leaching system placed in unsuitable soil, or a system too small for the house it serves or not properly constructed may lead to early failure. In most cases it will be necessary to install a new system to correct the condition.
2. SOIL CLOGGING
If sludge or from the septic tank is allowed to escape into the leaching system, the leaching system / soil interface will quickly become clogged and form a barrier to further penetration by effluent This condition can be caused by: broken baffles which allow the sludge to flow out of the tank, or failure to pump the septic tank out on a regular basis (2-5 years for a tank that meets the code) causing sludge buildup in the tank to the point where it washes over the baffles.
3. HIGH WATER TABLE
During wet seasons the groundwater table can rise into the leaching system area and sewage may be forced upward to the ground surface. This problem is usually the result of improper installation and can be corrected by relocating or raising the leaching area at least eighteen inches above the maximum high water-table. Another possible solution is to install ground water drains around the leaching area to lower the groundwater table if slope and soil conditions warrant.
4. TREE ROOTS
The roots of trees and bushes planted too close to the leaching area can sometimes enter and block the pipes of the system. removal of such plants is usually required.
5. HEAVY WEIGHTS OVER ANY PART OF SYSTEM
Trucks or heavy equipment passing over the tank or leaching system area can so damage connections, crush pipe and or compact the soil as to render the entire system inoperable. Being aware of the location of all elements of the system and directing traffic around them can prevent such damage.
DOS AND DON'TS TO KEEP YOUR SEPTIC SYSTEM HEALTHY
By following a few simple rules and procedures, the homeowner can help save his system against premature failure.
DO NOT put the following materials in your septic system:
MODERATE AMOUNTS of bleach and other household cleaners will not significantly interfere with the septic system's bacterial processes.
SPECIAL NOTE: DO NOT dig up an existing septic leaching system unless there is insufficient space to install a new system or expand the present one.
Before purchasing raw land or an existing property with a septic system...
It is my recommendation that you contact the local health department before purchasing: raw land to be developed for your dream house or business, or before purchasing an existing home or business that is using a septic system. They can provide you with information about the existing septic system and whom locally can do soil testing to provide you with a feasibility report on the property with regard to its ability to support a septic system on that property for the use you intend for it.