What is an indirect feed in water system design?

An indirect feed in water system design refers to a system that uses a holding tank to store water before it is delivered to the treatment process. This design allows for greater flexibility in managing water supply and treatment schedules. The presence of a holding tank enables the system to ensure a consistent and adequate supply of water, which can be particularly important in situations where water supply fluctuates throughout the day or when there are peaks in demand.

Having a holding tank also provides an opportunity for the water to have additional contact time with any treatment chemicals, allowing for improved effectiveness in the purification process. This design can also incorporate filtration or treatment processes while maintaining a stable flow of water to the point of use.

In contrast, designs with no holding tanks or those that involve direct water input do not provide this level of storage and may have limitations concerning water quality and availability. The method for reducing water hardness, while essential in many water treatment systems, does not directly define an indirect feed system. Therefore, the option highlighting a system utilizing a holding tank rightly identifies the key characteristic of an indirect feed design in water system engineering.