ANTIFREEZE HYDRAULIC CALC

[coarts]

Does nfpa 13 require a special calc using Darcy-Weisbach formula for antifreeze systems or is it just recommended? In a small attic system less than 40 gallons would the Hazen-Williams calc [we use hydracalc] be close enough?

 

[Oremus]

NFPA 13 2007++ requires antifreeze systems over 40 gallons to be calculated to DW in addition to HW. If you're under 40 you're good to go with just the HW.

Hydracalc can do DW calcs provided you're not using an outdated version.



22.4.4.5 Design Densities.
22.4.4.5.1* For antifreeze solutions greater than 40 gal (151 L) in size, the friction loss shall also be calculated using the Darcy–Weisbach equation shown in 22.4.2.1.3 using a Moody diagram, -factors that are representative of aged pipe, and adjusted K-factors for fluid properties.