Using ireducing elbow 1x1/2 nstead of elbow 1" + reducing coupling 1x1/2 in sprinkler system

[scythe13]

Hi,
I am involved in a sprinkler installation project. Currently we are installing sprinklers in the rooms, the pipes size is 1" and the sprinklers are installed above false ceilings, however the client wants the false ceiling height to be as low as possible.
As far as I know, to attach a recessed sprinkler to a 1" pipe, it is required to use a 1" elbow plus a reducing coupling 1x1/2.
I was wondering in order to reduce the connections size if it's possible to use reducing elbow 90 1x1/2 (which eliminates the need for the reducing coupling 1x1/2)? Does NFPA-13 says something in this regard?

 

[Oremus]

You can use a reducing elbow and that's fine but you usually don't see this for pendant sprinklers because using them doesn't allow you much flexibility in the field where the elevation of the branchlines will be adjusted to miss truss webbing, plumbing lines etc... all of which may turn a good intention into a nightmare - install wise.

 

[skdesigner]

Where are you going to hang the main if the branchlines are only 2" above the t-bar? Come off the bottom and trap everything?

You will also have a bit of a scrap with the ceiling guys when they realize that they can't wiggle the tiles into place. RC's are made onto the drops on the power machine, let the apprentices do their thing.