Why branch and tree is preffered?

[DavidCR]

I´ve found in a building specification for a sprinkler system that it must have a branch and tree configuration, and that gridded systems are not acceptable unless a especial approval is given.

Can anybody comment on why branch and tree configurations are preffered in a building specification?.

Thanks a lot in advance.

 

[louis]

I expect that what you have seen is a specification based on pipe schedule. The main and branch configuration is much simpler to design while producing an adequate system. The grid systems can be cheaper and more efficient (regarding materials), but require more complex calculations to ensure that the system will be adequate. It has been a long time since I looked at sprinklers, but I think NFPA 13 has an appendix designing by pipe schedule.

 

Perhaps the spec is for a dry pipe system. NFPA specifically states that grid systems are not allowed for a dry pipe system (takes too long for water to arrive at the heads).

Also, a tree system is easier to calculate and check.