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Heat waves and smoke signals: this month, questions range from fire pump sizing and protection, to placement level of in-rack sprinklers, to friction loss on check valves.

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Q: Do you have any friction loss data on older, single chock valves? I can't find much of anything. Our local building are having owners upgrade the headers to incorporate a backflow preventer. I don't really think it's fair to owners of buildings (that they have occupied for many years) to be required to upgrade their systems due to an added backflow preventer. Since many of the system are pipe-scheduled and a lot of times they don't work when calculations are performed, it requires time to figure out the new calculations and a lot of renovation.

A: Right, it's no laughing matter. The whole mess would be a lot easier to stomach if the retrofitting of a backflow preventer on a fire sprinkler system amounted to any kind of real benefit. While NFPA 13 (2007) includes a retroactivity clause (1.4) that grandfathers in the older sprinkler systems, it also requires in duplicitous fashion that (8.17.4.6.2) "a thorough hydraulic analysis" be performed "when backflow prevention devices are to be retroactively installed on existing systems," including as part of this exercise "all necessary system modifications to accommodate the additional friction loss."

All of this nonsense and expense could easily be averted if the code simply permitted an additional flanged check valve to be added to the existing system. This would add up to two check valves--the same thing you're accomplishing with...

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