A septic tank stores and treats wastewater contaminants like food waste, toilet paper and human waste. Keep grease, chemical drain openers, paint, solvents, fuels, chemicals, photographic solutions, pesticides and other organic chemicals out of the tank to prevent them from contaminating the soil and groundwater.
Don’t use enzyme or yeast additives to speed up bacterial action, they may actually kill bacteria. Regularly have the tank pumped and record all inspections, pumpings, repairs and permits. Visit https://www.septictankarmadale.com.au/ to learn more.
The wastewater that drains from our toilets, sinks and showers goes down the drains into the septic tank. This is a large underground tank made of concrete, heavy plastic or metal that holds the waste in a quiescent body of water. It is a primary treatment system for household wastes. It separates solids through a process of both settling and flotation. Substances that are lighter than water (oils, grease and fats) float to the top. Aerobic bacteria break down these floating substances, reducing their quantity and making them less toxic. The septic tank is divided into three layers: scum, sludge and effluent.
The septic tank must be regularly pumped to remove the accumulated sludge and scum. The septic tank must also be “de-slugged” to make sure all solids are removed from the wastewater leaving the septic tank. This prevents the septic tank from overflowing into the drain field and contamination of groundwater. The frequency of pumping depends on the size of the septic tank, how much is used in the house and what kind of materials go down the drains. Regular use of a garbage disposal and the flushing of items that don’t break down like wet wipes and paper towels may require more frequent pumping.
A septic tank can only be pumped to about a half full level. When this occurs, the solids that have accumulated will be forced into the drain field and clog the soil and gravel in the absorption area. This can cause the septic system to fail and the disease-causing organisms in sewage to leach into groundwater, contaminating well water and threatening human health.
It is important that solids are removed from the septic tank before it is pumped so that the septic tank does not overflow into the drainfield and infect groundwater and humans. The septic tank must also be properly installed, with consideration for hydraulics and the oxygen demands of the bacterial digestion.
The septic tank is not the place to drain surface water from the roof of your house, such as rainwater collected in guttering and downpipes. This should either go to a soakaway or stormwater attenuation system or into the main drainage network.
Sludge
When wastewater leaves your home or business, it runs into a septic tank where it’s partially cleaned. Solids sink to the bottom and form a sludge layer. Fats, oils, and grease float to the top where aerobic bacteria work to digest them. Liquids settle to the middle as a clarified liquid called effluent. Over time, the septic tank collects a layer of sludge that can build up to the point where it blocks the septic tank outlet pipe. This causes the septic tank to overflow and requires system repair or replacement.
When the septic tank overflows, it can contaminate groundwater and cause health hazards for those who live or work in the area. The septic tank must be pumped out to clear the line. To prevent this from happening, follow a few septic tank maintenance tips.
The “sinkable” solid waste materials (soil, grit, bones, unconsumed food particles) sink to the bottom of the septic tank to form a thick layer called sludge. Underwater anaerobic bacteria thrive in the sludge layer, giving off gases as they decompose organic waste material. Over time, the sludge layer will become even more dense as it settles to the bottom of the tank.
After the sludge is removed, the remaining liquid effluent passes out of the septic tank and into a perforated pipe that leads to the drain field in your soil. This pipe moves out the pre-processed wastewater over a specified area in your soil. The soil acts as a filter and further decomposes the remaining waste material through the action of microbes.
To reduce sludge accumulation in your septic tank, it’s important to only flush paper products and non-biodegradable toilet tissue. It’s also a good idea to regularly check the level of sludge in your septic tank with a septic tank monitoring device that uses a probe to monitor sludge levels. This is a better option than using a stick to check the sludge layer, which could damage your tank. A septic tank monitoring system will alert you when the septic tank needs to be pumped.
Scum
Substances lighter than water float to the top of your septic tank, forming the scum layer. These are mostly oils, fats and grease, along with some paper products that were flushed into the septic system. Aerobic bacteria in the septic tank digest this layer of floating waste materials, producing soluble compounds that enter the clarified effluent layer below. This liquid effluent makes up the majority of wastewater that flows from your septic system to your absorption field.
The septic tank is designed with sufficient volume to allow solid waste materials to remain in storage for some time, depending on household practices and how the septic system is used. However, solids will eventually accumulate and must be removed from the septic tank. This is when septic tank pumping becomes necessary.
If the septic tank is not pumped when needed, the accumulated sludge layer can enter the drain field and clog the outlet pipe, interrupting the flow of wastewater to the absorption field and causing costly system failure. Regular septic tank pumping keeps the sludge layer in check, extending the lifespan of your septic system.
During decomposition, the septic tank forms three separate layers: sludge, scum and effluent. Depending on household practices, the septic tank can develop these layers faster or slower than expected. Homes with larger households and more people using the septic system may see faster buildup of sludge and scum. High water usage can also accelerate buildup by flushing more solids into the septic system before they can break down, so be mindful of your home water usage.
Unlike sludge, the scum layer is primarily composed of organic materials that are biodegradable. As such, scum layers are less dense than the sludge layer and can be removed from the septic tank with relative ease. However, septic tanks require routine pumping to ensure that the sludge and scum layers do not exceed their design storage limits and enter your absorption field. This is important to prevent clogging and reduce leach field soil degradation.
Effluent
After wastewater leaves your home, it travels down a sewage pipe into your septic tank. When it reaches the tank, it will settle and the non-liquid components will separate. Heavy solids sink to the bottom, forming a layer of sludge. Lighter, floating materials like soap scum, FOG, and food particles form the scum layer. The liquid layer between them is called effluent.
As the septic tank fills up, the bacteria inside the tank begin to break down the solid waste material and turn it into a liquid. This process is known as anaerobic digestion. This occurs in two chambers of the septic tank that are separated by a half wall. Solid waste falls into the first chamber and starts to break down, while the liquid moves over the half wall into the second chamber. Once the sludge has melted away, the liquid effluent is ready to be discharged into the absorption field.
During normal operation, the liquid effluent will flow through watertight 4-inch diameter pipes from the inlet and outlet tees into your absorption field. These pipes should be sloped a 1/4 inch per foot to prevent clogging in the field.
It’s important to note that the septic tank and absorption field is not where you should be sending rainwater from your guttering or downpipes. That water must go to the stormwater drainage network, or a separate soakaway system (soakaway/rainwater attenuation tank).
Septic tanks are typically rectangular in shape and can be anywhere from 200 to 12000 gallons. They are designed to hold enough sewage for at least 2 days to allow time for solids and liquids to separate and pass into the drainfield. Tank size is usually based on the number of bedrooms in your home.
Generally speaking, septic systems work well and will not fail. However, there are a few common reasons that people need to have their septic tank pumped. The most frequent cause is when homeowners flush or rinse items that shouldn’t be sent down the drain, such as cooking oil, non-flushable wipes (such as baby or makeup removal), cigarette butts, cat litter, and pharmaceuticals. Also, the septic tank can fail to operate properly due to lack of pumping or maintenance, which results in the sludge and scum layers getting too thick.