If a septic tank is not pumped regularly, pathogenic bacteria and dissolved organic pollutants may reach nearby drinking water wells and local waterways. You may also notice a foul smell in your yard.
Septic Tank gathers wastewater from toilets, showers, and sinks and sends it to a buried drain field. Solid waste settles in the Tank, and liquids exit into the field through pipes.
When your home’s plumbing sends wastewater to the septic Tank, gravity causes the water to settle. Heavy solids sink to the bottom of the Tank, where bacterial action partially decomposes them. Lighter masses, such as fats, oils, and grease, float to the top of the Tank to form a scum layer. The clarified liquid between these layers, known as effluent, exits the septic Tank through a pipe to the drain field.
In the septic Tank, a healthy population of anaerobic bacteria eats away at organic waste in both the sludge and scum layers, liquefying them into smaller particles and gasses. This process removes most of the disease-causing organisms from your home’s wastewater.
The septic Tank is designed with enough volume to store sludge and scum for several years before needing pumped. However, it’s important to prevent overflow by reducing the amount of waste that enters the Tank. Overflow is costly and can cause wastewater to seep into the surrounding soil rather than being treated in the drain field.
Once wastewater leaves the septic Tank, it trickles from a series of perforated pipes through a layer of gravel and then into a deep bed of sand where it is further treated by soil. The soil removes any remaining disease-causing organisms and toxins from the wastewater, protecting groundwater in the area.
It’s important to protect the septic system by only flushing items that can be broken down or fully absorbed, such as toilet paper, paper towels, tissues, cotton balls, tampons, and menstrual hygiene products. Flushing non-biodegradable waste like cigarette butts, hair, food scraps, condoms, pet poop, and other debris can clog the drain field, causing it to overflow and leak wastewater into the surrounding soil.
Sludge
When water drains into a septic tank, it separates into three layers: scum, sludge, and effluent. The sludge layer is composed of the heaviest solid waste materials that do not decompose quickly. It settles at the bottom of the septic Tank and can block inlet and outlet pipes. This can lead to wastewater spills, system failure, and health issues. Pumping removes the sludge layer, allowing wastewater to flow freely from the Tank and into the drainage area.
A layer of substances that are lighter than water (oil, fats, and grease) floats on top of the wastewater in the Tank. Aerobic bacteria work to digest a majority of these floating solid wastes. However, if too much scum builds up, the bacteria become anaerobic and stop digesting waste. This can create noxious fumes and reduce the efficiency of your septic system.
In addition to clogged drains, a septic tank with too much sludge can cause wastewater to seep back into the house through its plumbing connections. Pumping the Tank prevents the buildup of sludge and scum, which ensures that wastewater spends enough time in the septic Tank for proper separation.
Careful, regular maintenance of your septic Tank is the key to keeping it in good shape. In addition to getting it pumped regularly, you can also do some of the work yourself by using a “wooden pole technique.” It’s a lot less intimidating than it sounds and is an easy way to check how much sludge your septic Tank has in it. Grab a long stick or wooden pole that you don’t mind ruining by dipping it into the primary septic tank chamber and mark where the sludge tide leveled off. This will tell you how many more times your septic Tank needs to be pumped.
Scum
As wastewater moves through a septic tank it naturally separates into three layers: sludge, scum and the bulk liquid layer. The sludge layer at the bottom of the Tank contains heavy, insoluble solids, such as fecal waste and toilet paper. The scum layer, at the top of the Tank, consists of fats, oils and greases which float above the water surface and where aerobic bacteria work to digest them. The bulk liquid, or effluent, flows through the septic tank outlet into the drain field or leach field.
Septic tanks are designed to allow gravity and flotation to separate solids from wastewater. Gravity allows heavier solids to sink while fats, oil and greases float. Aerobic bacteria in the septic Tank then digest these floating materials as they pass through the scum and sludge layers.
In addition, anaerobic bacteria in the sludge layer consume organic material from the scum and sludge and give off gases as they do so. The result is that these solids are liquified and are then carried away into the drainage field, where they are absorbed into the soil and groundwater.
In order to operate properly, septic tanks need an active and healthy microbial community. To achieve this, the septic Tank should be kept free from chemicals that impact the bacterial balance in these three layers. Chemicals that affect bacterial activity include laundry detergents, household cleaners, and personal hygiene products. In addition, septic tanks need to be cleaned out (pumped) on occasion. If septic tanks are not pumped regularly, the incoming sewage does not spend enough time in the Tank for solids to be sufficiently separated and may flow into the drainfield with a high volume of solids. This can lead to clogs in the drainfield, pathogenic disease-causing organisms and surface pollution.
Effluent
As the septic Tank fills up with solid waste, bacteria begin digesting and separating the waste materials. The sludge sinks to the bottom and the lighter solids, such as oils and fats, float to the top. This leaves a clear, wastewater-like liquid called effluent that is discharged to the drain field.
In some septic tank designs, such as the Imhoff tank, the sludge is digested in a separate chamber before it is discharged to the drainfield. This helps to prevent the sludge from mixing with incoming sewage and clogging the absorption field.
Once the septic system has treated the wastewater, it is discharged into a drainage field that contains a network of perforated pipes buried in soil, known as a drain field or leach field. The wastewater is then absorbed into the surrounding soil, where it is slowly released into watercourses and groundwater tables.
The septic Tank also retains solids that do not dissolve in the waste treatment process, such as human hair and other debris. It is important that the septic system retain these solids so that they do not flow out of the drain field, where they could clog pipes and create a health hazard to humans and animals. If these solids are not properly disposed of, they can contaminate groundwater and cause disease-causing pathogens to enter the surface water supply.
When the septic Tank is full, a company that offers septic tank pumping will come to the home and remove the sewage by using a truck with a giant tank and a giant suction hose. A septic tank should be pumped every three to eight years to ensure the sludge and scum are not taking up more than 35% of the volume.
Drain Field
After wastewater leaves your home, it flows into the septic Tank, where bacteria break down solid waste. Heavy solids sink to the bottom and form sludge, while lighter materials like oils and grease float to the top and form scum. The liquid, which is also known as wastewater or effluent, then exits the Tank through an outlet with a screen or filter to block larger particles. From there, it flows into a drain field or leach field.
Whether the wastewater is absorbed into the soil or not, the leach field is vital for the proper functioning of your entire septic system. It’s a series of downward sloped pipes with holes cut in them that extend from the septic Tank and spread outward across your property.
These pipes are designed to prevent wastewater from escaping into groundwater or running off into the environment. Instead, it’s filtered by the soil as it makes its way back into the water supply.
A well-maintained septic system can typically last between 20 and 30 years. However, improper usage or lack of maintenance can shorten its lifespan.
If your septic Tank needs to be pumped more frequently than usual, or you notice wastewater or sewage backup into your home, it’s time for a septic system replacement. Other signs include wet, soggy areas around the septic system and lush green grass growing over your drain field.
You can help the longevity of your septic system by using water-conserving appliances, limiting the number of loads of laundry and dishes you wash on a single day, and only flushing human waste and toilet paper. Doing so helps you avoid the risk of clogs and other problems that shorten its lifespan.