Septic Systems (Continued)
What to do if your system is failing
If your system exhibits one or more of the failure indicators, contact your county health official for assistance in assessing the situation. Some times the system may be able to be repaired without complete replacement. Sewage contains harmful bacteria, so keep pets and children away from the failure. Limit water use until repairs can be made. If a new system or repairs are needed, a permit is often required from your local health department.
General Maintenance Tips
Sound operation and maintenance practices include water conservation, keeping harmful substances out of the system, and having the system inspected and pumped on a regular basis. Good operation and maintenance practices start with everyone in the household knowing what damages the septic system. Having a diagram of the complete system indicating distances and locations of the tank and drain field helps avoid practices that can harm the drain field and assists in regular maintenance activities.
Maintaining the Septic Tank
Pumping the septic tank regularly is probably the single most important practice that can protect the system. The solids that settle out in the tank should be removed every three to six years depending on water usage and the amount of inorganic materials entering the system. A guide to follow with a 1,000-gal tank is to pump every three years for a household of four or more people and pump every six years for one with two people (increase times by one-half for 1,500-gal tanks). You also can determine when pumping is needed by opening the top of the tank and making some measurements and observations.
CAUTION: NEVER INSPECT A TANK ALONE, AND NEVER GO DOWN INTO A TANK.
Toxic gases are produced by the natural treatment processes in the tank and can kill quickly.) Pump the tank when the sludge layer at the bottom of the tank is 18 inches deep or the scum layer thickens to within three inches of the outlet baffle or sanitary tee outlet.
Solids should be removed by a certified tank pumper and disposed of in an approved manner and location. Be sure that the pumper removes all of the material in the tank. It is not necessary to leave some sludge to "restart" the biological processes; nor is it necessary to scrub or disinfect the tank.
When not removed in a timely manner, overflowing solids from the tank accumulate in the drain field clogging the soil and backing up the system. This damages the drain field and may require constructing a new drain field in a different location on the property. When the drain field is clogged with solids, pumping the tank does not rejuvenate the drain field. It provides only a few days of relief until the tank fills again and delivers wastewater to the drain field. Some clogging of soil pores occurs quite slowly even in a properly maintained system, but this should not cause system failure for 20 years or longer.
Maintaining the Drain field
The drain field is the most important component of a conventional septic system. It provides final treatment of wastewater. The more water used in the household, the greater the possibility of having problems with the drain field. Careful and regular maintenance of the tank extends drain field life.
Water conservation reduces the amount of wastewater delivered to the drain field. Keeping faucets and toilets from leaking with periodic checks and repairs certainly reduces wastewater. Do not allow foundation drains, roof gutters, and other surface waters to enter the septic system. Divert surface waters from flowing across the drain field and reduce surface water ponding above the drain field trenches by keeping soil levels at or slightly above the surrounding soil areas. Allowing heavy equipment to compact the soil above the trenches results in squeezing the soil pores which reduces water flow, increases clogging of pores, and reduces oxygen movement to the "active microbial zone" around the drain field lines. Oxygen is necessary for the microbes to properly convert pollutants to harmless gases that diffuse upward to the atmosphere. Without this conversion, the wastewater is not fully purified and the pollutants remaining can enter the groundwater.
Septic Tank Aids
These products are sold in many forms, but they do not reduce the need to regularly remove solids from the septic tank by pumping. Many of these products include bacteria, yeasts, enzymes, mild acids, mild bases, or biodegradable organic solvents that are not harmful to the septic system, but some will damage the tank or drain field or contaminate the groundwater.
Practices that reduce system function
Be aware of products or household systems that can damage or reduce the effectiveness of the septic system. Reducing garbage disposal use reduces the amount of solids going to the septic tank. The scum layer on top of the wastewater in the septic tank is primarily made up of oils, fats, and grease from the kitchen. When cooking oils or other types of oils enter the tank, they become part of the scum layer. Grease and fats (lard, beef tallow, butter, cheese, and cream) enter the tank and harden on the liquid surface. They can accumulate until they clog the tank inlet or outlet. When homeowners use hot water to flush grease or fat down the drain, it may pass on through the tank directly into the drain field lines where it can rapidly clog soil pores in the drain lines. Even though these products are organic in nature, they are decomposed so slowly by microbes that further wastewater loading from the tank only speeds up clogging. Placing even small quantities of pesticides, paint thinners, solvents, drain cleaners, poisons, and other harsh household chemicals into the septic system can kill the microbes in the tank and drain field that decompose solids and purify the wastewater. Unfortunately, some organic solutions are not treated in the septic tank and can flow directly into the drain field where they are not effectively treated by the soil before reaching the groundwater.
Why do Septic Systems fail?
- Water Usage
Using more water than the soil can absorb is the most common reason for failure. The sewage is forced to the surface or backs up into the house. This problem is often the result of one of two problems. Either the system is improperly designed or the result of a change in water use habits such as an increase in the size of the family or the addition of a water-using appliance.
- Physical Damage
Driving, paving, or building on top of a soil absorption unit can damage the field. Pipes can shift or be crushed and the soil compacted. Damage of this sort can make it difficult to locate the septic tank and prevents access for regular pumping. Tree roots can also clog the soil absorption field. Plant the area in grass, not trees or shrubs.
- Improper Design and Construction
Improperly designed and/or constructed septic systems are doomed from the start. These systems usually fail in a few months because they are inadequately sized, installed in impermeable soils, or not properly constructed. In Oregon, several inches of unsaturated soil must be present beneath the soil absorption system to a limiting layer. Temporary or permanent water tables, bedrock, or impervious soil are all considered limiting layers.
The soil is the most important part of the septic system and must be properly evaluated and protected. If the soil layer is too thin, the wastewater will not be treated before it enters the groundwater.
If the soil is too tight, it will not absorb all the wastewater, forcing it to the surface. The soil profile should be evaluated by a local health department sanitarian or a registered soil scientist to ensure that it is appropriate for wastewater treatment and disposal.
When constructing a septic system, it is essential that all components of the soil absorption field be level. If a line lies at too steep a grade or if the distribution system is not level, the wastewater will not be evenly distributed to all portions of the soil absorption field. This may overload one part of the field.
The heavy equipment used in home construction can compact the soil. During construction of the house, the area designated for the soil absorption system as well as the required replacement area and the area directly downhill should be fenced off to keep out heavy vehicles. Also, constructing and excavating a system during periods of high soil moisture can result in excessive soil smearing and compaction.
- Lack of Maintenance
The septic tank should be pumped about every 2 to 3 years to remove the sludge and scum retained in the tank and prevent clogging of the soil absorption field. More frequent pumping is needed if a garbage disposal is used in the home. Biological and chemical septic tank additives are not necessary and do not eliminate the need for pumping.
A septic tank is equipped with baffles at both the inlet and outlet. The inlet baffle prevents short-circuiting of the sewage and the outlet baffle prevents the floatable scum from moving out into the soil absorption field. In time, these baffles can deteriorate and drop off into the tank. The condition of the baffles should be checked when the tank is being pumped. Replace those in poor condition with sanitary tees.