Wet chemical systems discharge a limited quantity of agent, will not cause overflow, require less downtime, and are less costly to recharge. Surfaces coated with wet chemical agent must be cleaned as soon as possible with soap and water to avoid staining of appliances, keeping cleanup to a minimum. The installation of a water sprinkler system for restaurant cooking appliances is not always as simple as adding on to the existing sprinkler system that protects the remaining portion of the building. The piping configuration can be more complicated than wet chemical systems, especially in the duct area. Standard sprinklers or automatic spray nozzles are required at duct entrances, the tip of each vertical rise, and at midpoint of each duct offset.
Horizontal ducts require sprinklers every ten feet of duct.
Listed below are wet chemical pre-engineered systems that only require nozzles located at the duct entrance and they are listed for unlimited ducts. Sprinklers or automatic spray nozzles in the exhaust duct subject to freezing must be protected against freezing by insulating coverings, frost proof casings, etc. Wet chemical systems are dry pipe systems and do not require freeze protection of any kind. Access doors or panels must be provided for all sprinklers or automatic spray nozzles for examination or replacement. Wet chemical pre-engineered system nozzles do not require access doors or panels since all nozzles are accessible for servicing.