It seems that all of winter hit in one month — February. Are you particularly concerned about the large, unheated, remote warehouse you manage for your company in the Middle Atlantic region? Your company accepted your recommendation to install a dry sprinkler system in the warehouse because staff don’t go there until or unless stored items need to be moved and you were rightly concerned about the possibility of busted pipes when the temperature drops below 40°F. Since there is no standing water in the pipes, that system should not require as much routine maintenance as a wet or deluge system, right?
Pipes in an unheated space, particularly during periods when the ambient temperature and corresponding humidity fluctuate often, will have condensation. Frozen condensation can plug the system main feed or worse.
Dry systems are more susceptible to problems than are wet sprinkler systems. Why? Because the pipes are steel and, despite the fact that they remain “dry” due to air pressure in the pipes, the steel can and will corrode more quickly due to condensation.
Unattended facilities may also suffer from vandalism. Thieves search buildings for material such as copper; these criminals can and will damage pipes they hope will yield them cash.
You should establish a schedule for routine preventive inspection and maintenance of your dry sprinkler system. That system cost significantly more money to install than a wet sprinkler system; inspection and maintenance protect your company’s investment.
Dry System Maintenance
This primarily involves visual inspection and draining the drum dip as needed. You may also schedule ultrasound tests to ensure the viability of your dry sprinkler system.
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NFPA 25 (2011) provides maintenance standards and guidelines for you to use:
18.104.22.168 Maintenance, §22.214.171.124.2: Auxiliary drains in dry pipe sprinkler systems shall be drained after each operation of the system, before the onset of freezing weather conditions, and thereafter as needed.
§A.126.96.36.199.2: Removing water from a dry system is an essential part of a good maintenance program. Failure to keep the dry system free of water can result in damage and expensive repairs to both the system and building. A program for monitoring the condition of the system and the operation of the auxiliary drains should be instituted. Auxiliary drains should be operated on a daily basis after a dry sprinkler system operation until several days pass with no discharge of water from the drain valve. Thereafter, it might be possible to decrease the frequency to weekly or longer intervals depending on the volume of water discharged.
Likewise, when preparing for cold weather, the auxiliary drains should be operated daily with the frequency of operation decreasing depending on the discharge of accumulated water. In many cases, the frequency of the operation can decrease significantly if a system is shown to be dry. A quick-opening device, if installed, should be removed temporarily from service prior to draining low points.
Handbook Commentary: The low point drain in a dry pipe system is commonly referred to as a condensate nipple. The condensate nipple consists of a 1-ft length of 2-in. pipe with a 1-in. valve on each end. The upper valve is closed to isolate the condensate nipple from the dry pipe system. Next, the lower valve is opened to drain any moisture from within. Once draining is complete, the upper valve is opened to allow moisture to drain into the condensate nipple.