Which of the following is currently the most recommended water system for a computer room?

A.
preaction

B.
wet pipe

C.
dry pipe

D.
deluge

Explanation:
Preaction systems are similar to dry pipe systems in that the water is not held in the pipes, but is released when
the pressurized air within the pipes is reduced. Once this happens, the pipes are filled with water, but it is not
released right away. A thermal-fusible link on the sprinkler head has to melt before the water is released. The
purpose of combining these two techniques is to give people more time to respond to false alarms or to small
fires that can be handled by other means. Putting out a small fire with a handheld extinguisher is better than
losing a lot of electrical equipment to water damage. These systems are usually used only in data processing
environments rather than the whole building, because of the higher cost of these types of systems.
Incorrect Answers:
B: Wet pipe systems always contain water in the pipes and are usually discharged by temperature control–level
sensors. This type is not the most recommended water system for a computer room. Therefore, this answer is
incorrect.
C: In dry pipe systems, the water is not actually held in the pipes. The water is contained in a “holding tank” until
it is released. This type is not the MOST recommended water system for a computer room. Therefore, this
answer is incorrect.
D: A deluge system has its sprinkler heads wide open to allow a larger volume of water to be released in a
shorter period. Because the water being released is in such large volumes, these systems are usually not used
in data processing environments. This type is not the most recommended water system for a computer room.
Therefore, this answer is incorrect.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 474-475