mark handler said:
With the exception of unheated building spaces and freezer rooms, dry pipe systems do not offer any significant advantages over wet pipe systems. Their use in buildings is generally not recommended.
Dry sprinkler systems do have some problems.
Lack of maintanence is a contributing factor. So far this winter we have had 4 of our dry sprinkler systems freeze and break, one of them has frozen twice. One sprinkler room froze completly, including all the valves, the jockey pump, and the fire pump, and both risers. Each building that has frozen has not had the condensation drained properly. Those buildings with a competent maintanence program have not had a problem.
Installation standards need to be upgraded, concerning both the pipe used and insulation practices.
Schedule 5 and 10 pipe is used because it costs less to install. But 10 to 12 years later, we start replacing rusty pipe. On one repair job I gave the customer 2 choices. We could use schedule 10 or schedule 40. The schedule 40 increased the cost 10%. The customer spent the extra money. Now, we use schedule 40 exclusivly.
We often add auxillary drains to dry systems. We recently did a job and added 30 drains to dry system. The architect could have saved the building owner lots of money over the last 20 years by not having a 48" eave overhang. But the $21,000.00 check I got yesterday was nice.
Replacing rusty pipe is expensive. It may take 7 man-hours to remove and replace a stick of pipe.
Insulation needs to be addressed in NFPA 13. One of our clients had the roof insulated during the build. In 20+ years, We have not had to replace any broken pipes. They have a wet system with an antifreeze loop protecting a small patio and 2 dry heads. No dry pipe system. Another building has plastic tented over the dry piping in the attic, with blown insulation. The building has had no problem with frozen piping in 25 + years. We have had 3" wet pipe systems freeze because of lack of insulation. When a 3 " pipe thaws, everything gets wet!
