When is splitting flows prior to treatment by a sand filter permitted?

Splitting flows prior to treatment by a sand filter is permitted when subsurface disposal is used, as this method helps to effectively manage the wastewater that is being treated. Subsurface disposal systems are designed to handle effluent in a specific manner that allows for better treatment and distribution through the soil. When the flow is split before reaching the sand filter, it can improve the overall efficiency of the treatment process by ensuring that the sand filter does not become overloaded and can operate within its designed capacity.

This practice allows for the effluent to be distributed more evenly, which is crucial for the performance of the sand filter and helps maintain the integrity of the subsurface absorption field. By dividing the flow, it ensures that the filtered effluent can adequately infiltrate through the soil, promoting effective treatment and reducing the risk of system failure.

In contrast, the other scenarios presented do not align with the best practices for sand filter use and subsurface disposal. Flow splitting may not be allowed universally or applicable under conditions where appropriate management and treatment would result from a single flow, highlighting the importance of matching system design with operational practices.