The Septic Tank – The Heart of a Septic System

The septic tank is the heart of a septic system. It’s a large, buried water-tight container that holds wastewater from your toilets, kitchen sinks, showers and dishwasher. Depending on the size of your home, it may hold up to 1,000 gallons of waste. The tank has an inlet and outlet tees that connect to a drain field or absorption field, a shallow area of uncovered soil where bacteria in the ground naturally get rid of the sewage that leaves your house.

At the septic tank’s lowest point, weighty masses of solid waste sink to form a layer of sludge that is digested by anaerobic bacteria. Lighter masses, such as lint from synthetic fabrics and hair, and the oil and grease that wash down drains float to the top of the tank to create a layer of scum. For more information, Visit Our Website to proceed.

When the inlet and outlet tees open, the liquid wastewater called effluent flows into the drain field through perforated pipes that extend down into the soil. The soil naturally gets rid of the sewage by absorbing it through gravel and sand.

The septic tank must be emptied periodically to avoid overloading the drain field and causing overflows. Typically, the septic tank needs to be emptied every 12 months for small homes and up to twice a year for larger ones.

The best way to keep your septic tank running smoothly is to avoid flushing anything that won’t decompose, including flushable wipes, facial tissue, sanitary products, cigarette butts and cat litter. Also, don’t dump hazardous household chemicals or disinfecting cleaners into the septic tank or drain field.


Septic sludge is the solid waste that accumulates in a septic tank. It is created when gray wastewater (from kitchens or laundry rooms) and black wastewater (from toilets) are drained into the tank. As the wastewater settles in the tank, it separates into three layers: scum, effluent, and sludge. Scum is the top layer of the water, which consists of oils and fats that float to the surface. It is often comprised of soaps and greases that result from washing dishes, cleaning products, and washing hands. The middle layer is the wastewater, which contains waste particles and liquids. The bottom layer is the sludge, which consists of heavier waste solids that sink to the bottom. The sludge is decomposed by bacteria in the tank. It can take up to 24 hours for the bacteria to fully break down the sludge.

If a septic system is not properly maintained, the sludge may start to build up in the septic tank. This can clog the inlet and outlet tees, which will prevent wastewater from entering or exiting the tank. It can also clog the soakaway, which is a network of pipes that carry pre-processed sewage into the soils surrounding the septic tank.

Proper septic tank maintenance includes regularly monitoring and pumping the tank. Keeping the septic tank at or below 30% sludge is ideal. A septic tank that is over 30% sludge can cause septic tank leaks, clogged drains, and raw sewage backups in the home.

It is also important to know what not to flush, and to make sure that septic tanks are large enough to manage household waste. Typical items not to flush include paper towels, cotton swabs, dental floss, sanitary products, coffee grounds, pet feces, cigarette butts, and other waste that does not easily degrade. It is also important to never add commercial septic tank additives to the septic tank, as they can disrupt natural bacterial processes and the septic system.

With regular septic tank pump outs, proper septic tank maintenance, and the use of a biological digester such as Muck Munchers, you can minimize the risk of a septic tank sludge build-up. This can help to protect your septic tank and your home from costly repairs, replacements, or septic tank leaks.


As wastewater from your toilets, showers, bathtub, sinks, and washers drains into your septic tank, it undergoes a settling process. Solid materials like fats, oils, and soaps float to the top of your wastewater (scum), while debris, including paper and plastic wastes, sinks to the bottom of the tank, becoming sludge. Anaerobic bacteria in your septic tank then eat away at the sludge and turn it into liquid effluent.

When you flush your toilets or run water in your home, hydraulic pressure pushes the liquid waste out of your septic tank through the outlet tee into your septic system’s drain field. This forces the wastewater through a filter before it enters soil for further treatment. If scum or sludge is allowed to make its way to your drain field, it can clog the septic system and prevent wastewater from being properly absorbed by the soil.

A septic tank’s inlet and outlet tees are designed to prevent scum and sludge from entering the outlet tee and leaving your septic system. The inlet tee is usually elevated above the tank bottom and has a narrow vertical section that extends into the water. The top of this section is several inches above the bottom of the scum layer in the tank. The outlet tee is also designed with baffles to prevent scum and sludge.

Septic tanks are typically made from concrete, fiberglass, or polyethylene because these materials are sturdy and not prone to cracking while underground. If a septic tank cracks, waste will leak out and form puddles around the septic system’s drain field.

You can avoid problems with your septic tank and drain field by periodically checking the sludge level in your septic tank. If the sludge layer rises above the top of your tank’s inlet tee opening, you may need to add a bacterial additive or pump out your septic tank. If the tee is clogged, a professional can use a high-pressure pump to force water out of your tank. Adding the additive to your septic tank helps reduce odor and bacteria, as well as help break down solids in the septic system.

Absorption Field

When your septic tank is full, wastewater leaves through a pipe into an absorption field (also called a drain field or leach field). This is a series of underground gravel trenches that allow the wastewater to leak out and seep into the soil below. The soil functions as a filtration system and further treats the wastewater, reducing levels of harmful bacteria and other contaminants.

Sludge is a buoyant waste that floats on top of the liquid effluent in your septic tank. The inlet and outlet tees in your tank are designed to keep this sludge from exiting the septic system through these pipes, but if you don’t pump your septic tank regularly, this sludge can accumulate and clog your inlet and outlet tees as well as the pipes from the inlet and outlet. Sludge also may clog the drain field, preventing it from treating your wastewater properly and polluting groundwater.

Effluent that reaches the absorption field passes through a distribution box to ensure that the wastewater is evenly distributed over your drain field or fields. The distribution box may include multiple outlets or a series of parallel pipes that connect to each section of the drain field.

If the distribution box isn’t working as it should, it may be necessary to install a sump pump to remove the wastewater from the septic system to the drain field during heavy usage. You should never try to use a septic tank without a functioning distribution box and absorption field.

The size of your absorption field depends on the percolation rate of your soil. A percolation test is conducted by a licensed inspector who can recommend the correct size for your drain field. The rate is based on the amount of sand, silt and clay in your soil. Generally, a sandy soil has a higher percolation rate than a clay soil.

A seasonal high water table during rainy periods can saturate the soil, reducing its ability to accept wastewater from your house. Possible solutions to this problem include installing interceptor drains, lowering the water table with a lift pump or modifying your absorption field.