Which of the following is not a feature of dry pipe systems?

In dry pipe systems, water is not always present in the pipes; instead, the pipes are filled with pressurized air or nitrogen. This is a vital feature that differentiates dry pipe systems from wet pipe systems, where water remains in the pipes at all times.

The primary reason for using a dry pipe system is to prevent the water in the pipes from freezing in cold conditions. When a fire activates the system, the air pressure drops, allowing the dry pipes to fill with water from a remote water supply, which then is dispensed through the open sprinkler heads.

This system can be activated by smoke through a variety of detection methods. The use of smoke detectors to identify the presence of fire allows the system to respond quickly to potential hazards. The dry pipe design is also particularly well-suited for environments that are prone to freezing temperatures, ensuring safety during colder months.

Therefore, the correct understanding of a dry pipe system confirms that it does not have water present in the pipes until an activation occurs due to a drop in air pressure, allowing for effective fire suppression without the risk of freezing.