All, A couple weeks ago the topic of hydraulic loss through Mech Tee's was brought up. I was in agreement with most of the forum that the mech tee counts as a "fitting" and per the exceptions of NFPA 13, the fitting the sprinkler is attached to can be excluded from the calcs.
That got me thinking (which can be dangerous), how do you treat the scenario of attaching the sprinkler into a reducing bushing which is then screwed into a welded outlet or threaded tee. This is done all the time for a spec office or warehouse that has the potential for a future TI build out. If I want to take the code literally, I would ignore the loss in the bushing since that is the fitting the sprinkler is attached to. However, I would then need to add a short section of 1" pipe with a tee into my calc because it isn't directly attached. For a spec office this isn't that big of a deal as the change is minimal and probably forgettable based on all the other safety factors and constructability. However, if for whatever reason you are screwing a ¾" thread ESFR into a 1" outlet, the loss can be substantial. I was wondering how other people have treated this scenario. Never thought of it, ignore it, account for it, assume screwed fittings directly attached to each other equals "fitting" for NFPA 13 applications, etc. Thanks, Sean VG
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