Calc Run/Through Tees in NFPA 13 Residential?

10/3/2019

I have an inspector who wants me to prove that calculating run or through tees is appropriate for 13 Residential systems.

I showed them that run tees are in 13D, he thinks they should be calc'd in 13? How do I prove something is not in a code?

Any help would be appreciated.

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4 Comments

Jorge Diaz

10/3/2019 10:59:34 am

Is this what you’re looking for?
NFPA 13 23.4.4.8.1(5) Fitting loss for straight-through flow in a tee or cross shall not be included.

Wayne Ammons

10/3/2019 11:25:44 am

I think what he/she is asking is, since NFPA 13D (2019 Edition) Section 10.4.2.3(6) states that "The system shall be hydraulically calculated in accordance with the provisions of NFPA 13, except that the friction loss straight through a fitting shall be included", why wouldn't you have to calculate that loss in a 13R system?

NFPA 13R (2019 Edition) Section 8.2.1 states "Piping shall be sized using hydraulic calculation procedures in accordance with NFPA 13", without the stipulation to include the loss through straight-through fittings.

To me the argument seems pretty straight-forward, NFPA 13 (2019 Edition) Section 27.2.4.8.1(5) states "Fitting loss for straight-through flow in a tee or cross shall not be included", so in order to comply with the hydraulic calculation procedures in NFPA 13R, I would not include that loss as per NFPA 13.

Maybe someone can shed some light on why 13D would require the additional loss but 13R doesn't? Something to do with CPVC pipe and fittings maybe?

Shannon

10/3/2019 01:22:22 pm

10.4.2.3 refers to the use of 1/2" nonmetallic and copper piping. I've always read that section as "you only calc TRs if using PEX or flex copper".

Shawn

10/4/2019 09:19:27 am

If the fittings are CPVC the ID is reduced due to the way the fittings are constructed.

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Calc Run/Through Tees in NFPA 13 Residential?

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