Septic tanks break down solid waste through the process of anaerobic digestion. A series of perforated tubes then disperse the resulting wastewater into the nearby drainfield. Drainfields form a vital part of the septic treatment process. There, the waste safely percolates into the underground soil, which continues the process of breaking down potential contaminants.
Over the years, septic professionals have introduced many different styles of drainfields. Unfortunately, most homeowners fail to grasp the distinctions between different systems. This article takes a closer look at three common types of septic drainfields.
1. Gravity Drainfields
As its name would suggest, a gravity drainfield utilizes the power of gravity to move waste out of the septic tank. Gravity drainfields are one of the simplest styles of drainfield. To work properly, the level of the drainfield must lie below the level of the septic tank's outflow pipe.
As waste accumulates inside of the septic tank, it eventually reaches the height of the outflow pipe. At that point, the liquid moves down into the trenches of the drainfield. The drainfield's trenches contain gravel that allows for better dispersion into the surrounding soil.
Septic systems that use a gravity drainfield should be inspected at least every three years. Those who put off such inspections leave themselves at risk of serious problems. As sludge accumulates inside of the tank, wastewater has a harder time moving through the outflow pipe. Sewage backups, wet spots in the grass above the drainfield, and inexplicably slow drains may all ensue without proper inspection.
2. Pressure Distribution Drainfields
The geographical layout of a property sometimes makes gravity drainfields difficult — or even impossible — to install. High water tables, extensive rock layers, and other features of the landscape may prevent the necessary height difference between tank and drainfield. In such cases, contractors often suggest the installation of a pressure distribution drainfield.
A pressure distribution system differs from a gravity system in one key regard. Instead of gravity, a mechanical pump forces waste water through the outlet pipe into the drainfield. This pump turns on and off automatically through the movement of a float valve.
As wastewater levels rise, the float valve moves upward. Once the valve reaches a predetermined height, the pump comes on. As liquid flows out into the drainfield, the wastewater level falls once more. When the float valve drops below the cutoff height, the pump shuts down.
Pressure distribution septic systems require more regular servicing than gravity systems. A professional should inspect the tank and pump at least once per year. Otherwise, solid waste may cause the pump to become clogged. Likewise, waste build-up can prevent the float valve from working properly. If a float valve cannot rise freely, wastewater will eventually begin to overflow the tank.
Strictly speaking, a cesspool is not a septic system at all, although it does act as a type of drainfield. As discussed above, a septic system contains two distinct components: a septic tank and a drainfield. A cesspool, by contrast, collapses the functions of solid waste storage and liquid waste dispersion into a single structure.
A cesspool consists of an underground structure usually constructed of poured concrete or concrete blocks. Holes perforate the walls of the cesspool. These holes allow liquid to disperse into the soil around the cesspool, while solid waste accumulates at the bottom. These simple systems present serious drawbacks compared to more modern septic systems.
For one thing, cesspools require much more frequent maintenance. Otherwise sludge will block the holes, preventing water from dispersing into the soil. Even then, a cesspool has a much smaller dispersion range than a full septic system. As a result, backups and soggy lawns occur more frequently. Nonetheless, many older properties still contain cesspools.
To learn more about upgrading to a modern septic system, please contact the industry professionals at Chuck Keene Septic Tank Pumping Service.