In a properly working septic system, what is expected to be found in the leach field?

In a properly functioning septic system, the leach field is designed to receive completely treated wastewater. This treated wastewater, also known as effluent, comes from the septic tank, where solids settle at the bottom and are broken down by bacteria to leave behind relatively clean water. This effluent is then distributed throughout the leach field, which allows it to percolate through the soil.

The soil acts as a natural filter, further purifying the effluent before it eventually reaches the groundwater. It's important to note that the leach field must only contain treated, not raw sewage, which could contaminate the groundwater and cause health issues. The other options would indicate a failure in the septic system. For instance, raw sewage presents a significant health risk, while drinking water in the leach field could lead to contamination. Heavy sludge in the leach field signifies inadequate treatment and could cause system failure. Hence, the presence of completely treated wastewater is what one would rightly expect to find in a properly working leach field.