Why is it crucial to monitor solid levels in a septic tank?

Monitoring solid levels in a septic tank is crucial primarily to prevent overflow and system failure. As solids accumulate in the tank, they can reach a point where the tank cannot effectively separate solids from liquids. If the solids rise too high, they can overflow into the outlet baffle and then enter the drain field. This can cause several issues, including clogging of the drain field, which is designed to filter effluent, and potential environmental contamination due to untreated waste being released into the groundwater.

Preventive measures, including regular monitoring and maintenance of solid levels, help ensure the septic system functions properly and prolongs its lifespan. This upkeep is essential to maintain the effectiveness of the system's treatment capabilities and to avoid costly repairs that could arise from system failure, such as the need for a complete system replacement or major excavations.

The other aspects mentioned in the options, while relevant to septic system maintenance and effective operation, do not address the immediacy of overflow and system failure as directly as monitoring solid levels does.