fire sprinkler return bend

[cdafd]

1. nfpa 13 does not seem to say anything on the length a drop can be after the return bend

just wonder if any thoughts about that.

this is on a pre action system


any thing in the code about having to drain each drop after a trip??


any other thoughts about return bends???

 

[SprinklerDesigner2]

No length limit.

Must be installed in non-freeze environment.

Single sprinkler does not have to be drained.

 

[NJ1]

I agree with SprinklerDesigner2 however if you consider yourself a top designer I suggest keeping the branch as low as possible to allow proper drainage. Is not required but it says a lot about your design experience. This way less water will remain in the drop.
This is just a constructive opinion.

 

[RainbowFS]

I've always viewed goosenecks as a design compromise at best.
Isn't the shape of the return bend supposed to function as air trap and thus keep the drop from filling with water in most cases?
I try to avoid using them wherever possible.

Alex Traw
Rainbow Fire Sprinklers
Albany, Oregon

 

[NJ1]

I ma not sure about that RaimbowFS. In my 17 years of experience I allways found water in the drop however as I said before if branch is kept as low as the RC it will drain properly.

 

[spkreng]

All drops have water in them, the size of a drop on a pre-action system, by prudent design should be as short as possible, this is best accomplished by the length of the riser nipple off the line or main being as short as possible, if pitched then varied in length, which is not actually required in a heated space, pitching that is.

spkreng, CET

 

[RainbowFS]

I should have phrased my comment better, because I do realize that the drops always get water in them. I meant to say that the theory of goosenecks is to keep water out of them by trapping that little pocket of air. That's what I learned way back when, anyway.

Alex Traw
Rainbow Fire Sprinklers
Albany, Oregon