Why is a wet standpipe with a Siamese connection considered most practical?

A wet standpipe with a Siamese connection is particularly practical because it is served by the domestic water supply under constant pressure. This means that the system is always ready to deliver water quickly and efficiently when needed, especially during firefighting situations. The constant pressure ensures that firefighters can immediately access water without the delay of having to fill the system or worry about water availability.

This configuration allows for the rapid deployment of water at fire scenes, enhancing the overall safety and effectiveness of firefighting efforts. The Siamese connection is designed to allow multiple fire hoses to be connected and used simultaneously, providing a robust means of combating fires in larger buildings or areas.

The other choices do not accurately capture the primary advantage of a wet standpipe system. The manual operation would be a disadvantage in emergency situations; ease of installation isn't the primary reason for preferring this system; and while reducing water usage can be beneficial, it does not directly speak to the operational effectiveness that a constant water supply brings during a fire emergency.