What characteristic must a septic tank have regarding seasonal groundwater?

A septic tank must be watertight to above seasonal groundwater to ensure that effluent is properly contained within the tank and does not leak into the surrounding soil and nearby water sources. This characteristic is crucial for preventing contamination of groundwater from the septic system, which can pose significant health risks and environmental concerns.

When a septic tank is watertight up to the seasonal groundwater level, it ensures that even during periods of heavy rainfall or flooding, the tank remains secure and functional. If the tank were to be permeable or not watertight, it could allow groundwater to infiltrate the tank or treated effluent to escape into the environment, leading to potential pollution and system failure.

Maintaining the integrity of a septic tank and keeping it sealed above the seasonal water table is vital for the effective operation of the system and the protection of public health.