Septic Tank Systems Explained

Ever wondered how a septic tank system works? The article below details how septic systems work, how to maintain them and how to tell if something is wrong with your septic tank system.

septic tank systems

Example of a septic system

Septic systems have been in use for along time and are very reliable. Here are some of things you’ll need to know:

On average, septic systems have an estimated life span of about 20 to 30 years. A properly constructed and maintained system may last longer. A system that is not maintained can fail in 2 years or less. Regular maintenance protects the investment and avoids replacement costs. Maintenance also protects the health of your family, the community and the environment.  When systems fail, inadequately treated household wastewater is released into the environment. This can contaminate nearby wells, ground water, and drinking water sources. Any contact with untreated human waste can pose significant health risks.

Four very important principles to follow are:

  1. Don’t overload your septic tank system with extra water;
  2. Know what you can put in the system and what not to flush into it;
  3. Pump the septic tank on a regular basis;
  4. Do not disturb the tile bed / leaching bed /drain field e.g. by driving on it or planting shrubs on top of it.

A conventional septic system consists of two main parts: the septic tank and the drainage field (also referred to as a 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 works?

The Septic Tank — A septic tank is a large, underground, watertight container that is connected to the home’s main sewer line. The size of the tank is determined by things such as the size of the home, the number of bedrooms and bathrooms in the home. Septic tanks are made of concrete, fibreglass or polyethylene (plastic).

The untreated wastewater flows from the house to the septic tank where the solids separate from the liquid over time. The lighter solids, like soapsuds and oils / fats, float to the top and form a scum layer in the tank. Over time this layer continues to thicken until you have the tank cleaned. The liquid waste however goes out to the drainage field, while the heaviest solids settle to the bottom of the tank where they are digested by bacteria. The solids that do not decompose and remain behind form a sludge layer that eventually must also be pumped out.

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.

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 network of pipes is laid in gravel-filled trenches or beds in the soil. The liquid waste or effluent flows out of the tank and is then evenly distributed into the soil through the piping system. 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 depends on the estimated daily wastewater flow and soil conditions.

When should the tank be pumped out? This depends on a number of items including: the size of your tank, the number of people in the household contributing to the volume of your wastewater, and, the volume of solids in your wastewater. Generally, the tank should be pumped out every two to five years although a larger tank and smaller household may function longer without requiring pumping.

How do you know when something is wrong with your septic system? By far the most common reason for early failure is improper maintenance by homeowners. When a system is poorly maintained and not pumped out on a regular basis, sludge builds up inside the septic tank, then flows into the drainage field, clogging it beyond repair.

Here are some of the warning signs that may indicate a failing septic system:

  • The soil in the drainage field area is wet or soggy
  • 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.

Should a septic system be inspected when buying or selling a home? A septic system evaluation should be conducted as soon as the property is placed on the market so that necessary repairs can be made to the system if required. Failing this, an inspection should definitely be done as a condition of your “Offer to Purchase”.

At a minimum, the inspection should include:

  • The location, age, size and original design (if records are available) of the septic system
  • The soil conditions, drainage, seasonal water table and flooding possibilities on the site where the septic system is located
  • The history of the system (if records are available)
  • The condition of the plumbing fixtures and their layout to determine whether structural changes have been made to the plumbing that would increase flow to the septic system above capacity
  • System components that could affect the system, for example, water softeners draining to the septic tank or the presence of footing drains should also be inspected
  • Slow-flushing toilets and slow drains may indicate a failing system
  • The date the septic tank was last pumped (if records available)
  • The sludge level in the septic tank if it has not been pumped out recently
  • The condition of the drainage field. Look for evidence of liquid waste reaching the soil surface, draining toward nearby lakes and streams, or clogging the soil and gravel beneath the field. (This usually requires digging up a small portion of the drainage field.) Look for signs of heavy equipment that has been on the drainage field, causing compaction and possible damage.

Maintaining Your Septic System

Septic system maintenance is simple:

  • About every 2 to 5 years have the solids pumped from your tank
  • Conserve water usage
  • Don’t dispose of anything that can easily be put into the trash
  • Avoid putting coffee grounds, grease and cooking oils down the drains
  • Use toilet paper that is biodegradable and approved for use in septic systems
  • Don’t plant trees within 6 feet of the septic system. Don’t allow anyone to drive over or park on the septic system
  • Don’t allow livestock over 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
  • Don’t repair the septic system without obtaining the required permits from authorities having jurisdiction in these matters
  • When making repairs, use a licensed septic contractor
  • If you must inspect the septic system use appropriate caution…toxic gases from the tanks can kill in minutes. Better yet, hire a licensed professional
  • Make an accurate diagram showing the location of your septic tank and drainage field
  • Keep accurate detailed records of pumping, inspection and other maintenance carried out
  • 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, drainage field
  • Do not flush items that are not biodegradable.

Should you use additives with your system or not? 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 a homeowner is not misusing the septic system then these products will likely be of no benefit. The quantity of material added with each dose of these products is very small compared to the biological material already present and working in the tank.

Sometimes, your system can be upset when the septic tank bacteria are harmed or destroyed. This can happen if the home is vacant for a long period and the tank receives no fresh wastewater, or if strong cleaning agents are flushed down the drain. After a few days of normal use, the biological system in the tank will re-establish itself. In this situation the biological additives may help speed the recovery of the septic tank.

Every septic tank needs to be pumped periodically, because all wastewater contains inert matter that cannot be degraded in the tank. No additive can do away with this need.

Could an additive harm your system? — The biological additives are unlikely to be harmful. The chemical additives could definitely harm your system. These products have the potential to sterilize your system temporarily. The resulting passage of raw sewage into the drainage field will hasten its failure. The acid and alkali products can corrode the plumbing and the tank. The organic solvents pass through the system unchanged. They can then infiltrate into the groundwater, creating additional problems.

Source: Grassroots

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