What scenario requires the use of two monoflow tees in a down feed system?

The use of two monoflow tees in a down feed system is primarily needed in scenarios characterized by high piping resistance. Monoflow tees are designed to facilitate the flow of water in a specific direction while allowing return flow without mixing the two streams. When there is high resistance within the piping system—due to factors such as long runs of pipe, numerous fittings, or a greater number of connected fixtures—two monoflow tees are often necessary. This configuration effectively mitigates the impact of resistance and ensures adequate water circulation by allowing for an efficient path for both supply and return water, thus maintaining the system's performance.

In contrast, a single system loop would typically function with just one monoflow tee, as the flow is more straightforward and doesn't require additional support to overcome resistance. Low water velocity can also be managed with a single tee, as the flow rate is less demanding. Extended length piping, while it does introduce some resistance, does not inherently require two monoflow tees unless the specific system conditions warrant the need for enhanced flow management.