Septic Tank Systems
Septic tank systems are very reliable
A septic tank is a watertight chamber made of concrete, fibreglass, PVC or plastic, through which domestic wastewater (sewage) flows for primary treatment. Settling and anaerobic processes reduce solids and organics, but the treatment is only moderate. Septic tank systems are a type of onsite sewage facility. They mostly found in rural areas not connected to a sewerage system. The treated liquid effluent is commonly disposed of in a septic drain field which provides further treatment.
Most septic tanks have an estimated lifespan of 20 to 30 years. If properly constructed and maintained they may last longer.
A septic tank can fail within two years if not properly maintained. A failing septic tank does not adequately release household wastewater, polluting the immediate environment as a result.
Important to remember with a septic tank:
- Do not overfill your septic tank with water;
- Know what and what not, can be put into the system;
- Pump the septic tank on a regular basis;
- Do not disturb the tile bed/leaching bed /drain field by driving on it, or planting shrubs on it.
A conventional septic system consists of two main parts:
- The septic tank
- The drainage field (also referred to as the leaching field. At the head of the drainage field a distribution box, or a manifold, distributes wastewater to several absorption trenches).
How does the system work?
The Septic Tank
A septic tank is a large, underground, watertight container. The home’s main sewer line discharges into it. The number of bedrooms and bathrooms in the home determines the size of the tank.
Untreated wastewater flows from the house to the septic tank. Solids and liquid then separate. Lighter solids, e.g. soapsuds, oils and fats etc, float to the top and form a scum layer. Over time this layer thickens, at which point the tank has to be cleaned.
Liquid waste is discharged into the drainage field. Bacteria digest the heavy solids on the bottom of the tank. Undecomposed solids form a sludge layer on the top. The sludge layer will need to be pumped out from time to time.
The Drainage Field
Treatment of wastewater continues beneath the soil in the drainage field. The drainage field typically consists of long underground perforated pipes or tiles connected to the septic tank. The piping system distributes the liquid waste into the soil. The soil below the drain-field provides the final treatment of the septic tank effluent. After the effluent has passed into the soil, most of it percolates downward and outward, eventually entering the groundwater. The size and type of drainage field depend on the estimated daily wastewater flow, as well as the condition of the soil.
Modern septic tanks have two compartments. Baffles at the tank’s inlet pipe slow the incoming waste products and reduce the disturbance of the settled sludge. Another baffle at the outlet keeps the solids or scum in the tank. All tanks should have accessible covers for checking the condition of the baffles and for pumping out both compartments.
Pumping out the tank
This depends on the size of your tank and the number of people in the household. Normally the tank s pumped out after 2 to 5 years.
How do you know when something is wrong with your septic system?
A poorly maintained system builds up sludge if not pumped out regularly. It will clog the drainage field beyond repair.
Here are some of the warning signs that may indicate a failing septic system:
- Wet or soggy soil in the drainage field area.
- Grass grows greener or faster in the drainage field area.
- Sewer gas (methane) odours in the house or yard.
- Plumbing backups into the house.
- Slowly draining sinks and toilets.
- Gurgling sounds in the plumbing.
Have a septic tank inspected when buying or selling
As soon as you place the property on the market have a septic system evaluation. At this stage, make repairs if required.
If you are buying, an inspection should be a condition of your “Offer to Purchase”.
An inspection should at least include:
- The location, age, size and original design (if records are available) of the septic system.
- The septic system site soil conditions, drainage, seasonal water table and the possibility of flooding.
- The history of the system (if records are available).
- Additions and alterations to the plumbing which may increase flow to the septic system, above its capacity.
- Slow-flushing toilets and slow drains may indicate a failing system.
- The last pump out date (if records available).
- The level of sludge if not recently pumped out.
- The condition of the drainage field, e.g. evidence of liquid waste reaching the surface or draining toward nearby lakes and streams. Clogging of soil and gravel beneath the field requires a portion of the drainage field to be dug up. Look for signs of heavy equipment that may have been used on the drainage field. This could have led to compaction and damage.
Maintaining Your Septic System
Septic system maintenance is simple:
- Every two to five years have the solids pumped from your tank
- Conserve water usage
- Anything that belongs in the trash should not be in your septic tank.
- Avoid putting coffee grounds, grease and cooking oils down the drains
- Use approved toilet paper that is biodegradable.
- Don’t plant trees within 2m of the septic system.
- Don’t allow anyone to drive over or park on the septic system
- Keep livestock away from the septic system.
- Don’t cover the drainage field with concrete or asphalt. Grass should be the only cover
- Don’t pour harmful chemicals or cleansers into the system
- Obtain the required permits from authorities having jurisdiction, before carrying out repairs to the septic system.
- A licensed septic contractor should only carry out repairs.
- When inspecting the septic system use appropriate caution. Toxic gases from the tanks can be deadly!
- Make an accurate diagram showing the location of your septic tank and drainage field
- Keep accurate detailed records of pumping, inspection and other maintenance
- To simplify tank access for inspection and maintenance, install a watertight concrete riser over the septic tank
- Do not plan any building additions, pools, driveways, or other construction work near the septic tank or drainage field
- Do not flush items that are not biodegradable.
Should you use additives in your system?
Chemical additives are strong acids or alkalis, or organic solvents. Biological additives are cultures of harmless bacteria, plus waste-digesting enzymes. These sometimes contain yeast cultures.
If you are not misusing the septic system, these products are of no benefit.
If bacteria in the septic tank are destroyed the system will fail. This usually happens when the septic tank is not filled with fresh water for an extended period.
Strong cleaning agents kill bacteria. However, after a few days of normal use, the biological system in the tank will re-establish itself. Biological additives may help speed the recovery of the septic tank.
A septic tank must be pumped out from time to time. All wastewater contains non-degradable inert matter. Only pumping can get rid of this.
Could an additive harm your system?
Biological additives are unlikely to be harmful. However, chemical additives will definitely harm your system. They can temporarily sterilize your system. Thereby raw sewage enters the drainage field, causing its failure.
Acid and alkali products can corrode the plumbing and the tank. Organic solvents then pass through the system unchanged, infiltrating the groundwater.
adapted from an article by Rainharvest.co.za.