A septic tank holds all the wastewater from your toilet, kitchen sinks, showers, and washing machine. Solid waste settles at the bottom of the tank, fats float to the top, and liquid wastewater leaves the tank through an outlet pipe in your drain field.
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Despite being buried underground, the septic tank is often an ignored component of the home. That is, until the septic system isn’t doing its job and sewage starts backing up in the home. The tank is a vital part of the septic system, but like any other piece of equipment, it needs to be maintained and inspected regularly.
Wastewater flows from the house into a septic tank, where it separates into three layers: a sludge layer, a wastewater layer and a scum layer. The weight of solid waste causes it to sink to the sludge layer, where bacteria do their best to break it down. The scum layer floats above the sludge and contains oils and grease. Eventually these materials enter the drain field and can cause problems with the soil, waterways and groundwater.
The inlet and outlet pipes are both fitted with baffles to control what enters and exits the septic tank. The inlet pipe baffle prevents solid particles from entering the septic tank, while the outlet pipe baffle reduces the amount of sludge that enters the absorption field. Both of these are important to keep the septic system functioning properly and avoiding costly repair bills.
An inspection hatch is located over both the inlet and outlet devices, which allows for cleaning or determining the amount of sludge left in the tank. It is important to never allow anyone other than a professional to pump the septic tank through the inspection port, as they may damage the baffles and incompletely remove waste from the tank. Instead, the tank should be pumped using industrial vacuums, which can thoroughly clean and remove waste from every crevice of the septic tank.
A septic system vent is also installed at the septic tank and moves air out of the tank and into the leach field. The vent must be placed above the ground level to avoid the infiltration of rain, snow or small animals into the septic system. The vent must also be properly capped to reduce the risk of odors in the home or garden.
Exit Baffles
The inlet and outlet baffle walls are the unsung heroes of your septic system. They play a critical role in processing your wastewater on a daily basis, ensuring that solid waste stays inside the tank and only partially treated water exits.
In older septic tanks, baffles were often made of concrete. However, newer systems are typically constructed of plastic, which is more durable and has a much higher life expectancy than concrete. Regardless of material, your septic tank baffles need to be regularly checked and maintained for proper function.
The inlet baffle, which is located where the wastewater line enters the septic tank from your home, prevents floating solids such as grease and scum from getting above the liquid surface of the tank. This ensures that the septic tank can treat these solids thoroughly before they enter your home’s sewer lines, reducing the risk of costly blockages in those pipes down the line.
Once the solids are treated, they move to the outlet baffle where they’re separated from the more clear wastewater. This allows the more clear wastewater to flow out of the septic tank to your drain field, while keeping the more solid waste behind in the septic tank where it can continue to be digested by helpful bacteria.
As time passes, the inlet and outlet baffles can get damaged, or even become dislodged from the septic tank itself. If this occurs, it’s important that you call a professional right away. Dislodged or damaged baffles can cause wastewater to leak out of the septic tank and into your yard, which can be expensive to fix.
Other warning signs that your baffles may be in need of attention include slow draining and foul odors, which indicate that your wastewater is not being properly processed on a daily basis. Keeping up with regular septic tank pumping and inspections can help you identify issues such as these, as well as catch problems like broken baffle walls before they lead to more serious and expensive repairs.
Distribution Box
The distribution box is a small, round or rectangular container that is used to distribute the septic tank effluent to the pipe networks that disperse wastewater in the drain field. It is usually located underground between the septic tank outlet pipe on one end and a series of pipes leading to the drain field on the other end. The septic tank distribution box is a key part of the septic system that ensures uniform distribution of wastewater throughout the entire drain field.
Like all the other parts of your septic system, the septic tank distribution box needs to be regularly inspected and maintained to avoid problems. Most homeowners are familiar with the need to have their septic tank pumped every two to five years, but there are many other aspects of your septic system that need regular attention.
Septic tank distribution boxes can be made of fiberglass, plastic, or concrete. The longevity of the box depends on how well it is installed, the type of septic tank you have, and the quality of materials. For example, a concrete septic tank distribution box will last longer than a plastic or fiberglass box.
Keeping your distribution box free of debris is essential to its function. A clogged distribution box can lead to the overflow of wastewater into the yard, a blockage of your plumbing, and odors throughout your home. To avoid this, routine septic tank pumping and inspections can help keep your septic tank distribution box clean.
As bacteria in the septic tank break down wastewater contaminants, they release gases. These gasses must be vented to prevent a build-up of pressure that could damage the septic tank or other parts of your septic system. The septic tank vent has a mushroom-shaped cap that allows the gases to escape.
The septic tank distribution box is designed to be at the same elevation as the septic tank, but it’s important that it is not placed too far below ground level. If the box is too low, it can be buried in soil that may not be strong enough to support it. This could lead to cracking and structural issues that require repair.
Absorption Field
Once the liquid effluent leaves your septic tank, it moves into a drain field or absorption field. This is where the wastewater is further treated and absorbed into the soil, and from there into groundwater or surface water sources. The soil is an important part of the system, as it serves to destroy pathogens, degrade organic materials and act as a physical, chemical and biological filter for the wastewater.
Once in the absorption field, the solids that did not float to the top of your septic tank or sink to the bottom form a sludge layer and are further digested by bacteria. The sludge is periodically discharged from the tank into the absorption field. Without the septic tank, solids would pass directly into the absorption field, where they could clog and damage it.
In the absorption field, a network of perforated pipes is set in a series of shallow trenches, with clean soil placed beneath, above and around them. This soil is designed to be able to handle the wastewater volume from your septic tank, and is tested during site selection for suitability.
The absorption field pipes are fitted with baffles or sanitary tees, made of acid-resistant concrete, cast iron or plastic, which ensure that floating scum and sewage cannot plug inlet and outlet pipes. Six-inch diameter inspection pipes extend from these tees to the ground surface to allow for checking on solids levels and potential clogs.
If your septic tank and absorption field are poorly designed or improperly installed, the resulting waste can pollute nearby water resources. To reduce this environmental liability, state legislation sets minimum construction, design and permitting standards for onsite sewage systems. Homeowners should consult with a county health department sanitarian or building regulations department prior to any construction of a new septic system.
Other types of septic system can be used when state-approved septic tanks are not practical, such as in rock or clay soils. Alternatives include a cesspool, drywell, nitrate trap, sand and gravel filter or mound. These systems must meet minimum performance standards, and homeowners should consult with a county sanitarian before selecting an alternative.