Each filter installed after October 1, ________ must have facilities allowing filter draining without removing other filters from service.

The correct answer is based on regulatory changes implemented by the TCEQ (Texas Commission on Environmental Quality) regarding the design and maintenance of filtration systems. Specifically, filters installed after October 1, 2000, are required to have facilities that allow for draining without the need to take other filters out of service. This requirement aims to enhance operational efficiency and ensure that maintenance can be performed without compromising the entire filtration system's functionality.

This regulation reflects an awareness of the need for improved management practices in water treatment facilities, promoting better control over the filtration process while minimizing downtime and maintaining continuous service. The choice of the year 2000 is significant as it marks a pivotal point in regulatory development concerning water treatment technologies and infrastructure requirements.