I'm working my way through an automatic "wet" sprinkler design for an Ordinary Hazard Group 2 area. I'm having trouble definitively determining whether to use the pipe schedule method or the hydraulic method (7-2.2 & 7-2.3 in NFPA 13) to determine water demand.
It seems to me that sometime in the past I read that the hydraulic method was "preferred" by most modern designs, but can't recall the source of that comment. I've read and re-read NFPA 13 for clues as well as the Fire Protection Handbook from NFPA, but can't seem to find the reference.
For previous designs, I've used the Hydraulic Method and have spreadsheets already set up to assist me. But it seems that the pipe schedule design is a quicker, "cook book" design approach. One advantage of the Hydraulic method is that the water demand typically appears to be smaller (i.e. lower flow rate). This can be a bit of a concern in most of my designs, as the areas I deal with don't typically have access to "public water" and therefore the water must be supplied and "dedicated" to the fire suppression system by the owner of the property. This dedicated water supply costs money so the lower the flow rate, and the lower the total volume, the lower the costs.
I'm trying to develop a design guideline for myself (and my company) so that I don't have to wrestle through these comments every time I do a sprinkler design (every couple of years it seems).