Septic tank systems are composed of four basic components: source, septic tank, drain field, and the soil beneath it. Inappropriate conditions, design, or installation, and physical damages to at least one of the four basic components of septic tanks result in failure of the system. Problems such as sewage back up, slow draining, and wet smelly patches of water appearing in your yard are caused by failures in your septic drain field. Here are some of the reasons for a failing septic drain field and the need for septic tank repair:
The soil beneath your septic drain field is the most important component of the system. First, the soil condition must be appropriate for sewage. In general, sandy soils can absorb more wastewater compared to soft and clayish soils. Thus, areas with clayish soils require wider septic drain field compared to areas with sandy soils. Secondly, the location of the seasonal high water table or restrictive layer should dictate the depth of drain field trenches. If the restrictive layer is too close to drain field's surface, the wastewater may not be adequately treated before it reaches the groundwater. Consider soil condition when designing the septic tank system.
The source of water, as a component of the system, is also important. A septic system can't hold more water than what it was designed to have: 120 gallons per bedroom per day. Excessive wastewater either backs up to the house or surfaces in the yard. A leaky toilet, dripping faucet, or a sudden change in the usual water consumption result to exceeding the average wastewater flow rate. Excess water from outside the house such as rain or any water flowing off from the road or paved areas can also overload your septic drain field. Always repair leaky fixtures and protect your septic tank from unnecessary large amount of water.
Your septic tank system may be underneath your yard, but it remains vulnerable to physical damages caused by driving, paving, or building a structure on it. With excessive weight on top of the system, the pipes and tanks may change position and fail to bring water to your drain field. Even tree root systems can clog drain lines and allocate space in your drain field that is supposed to be for treating wastewater. So, avoid putting up structures and planting trees above the septic drain field.
In sum, shallow and clayish soil in the drain field, excessive wastewater overloading the drain field, and physical damage from excessive weight above and roots occupying the drain field are some of the causes why your septic tank is failing.