TravisMack
Mechanical
- Sep 15, 2003
- 1,752
This is truly a question for a friend 
When doing a large apartment complex per NFPA 13R (say 16 buildings where each are appropriate for 13R) that is supplied by a common fire loop, what do you do for the domestic allowance? This particular site had a domestic booster pump placed on the site for the domestic/fire loop. The sprinkler demand is 80 gpm +/- for the 4 residential sprinklers.
Since this is a domestic/fire loop 13R states that you have to figure a domestic allowance. My conservative nature says that you should figure the domestic load for each building on site and include that in the loop with your fire sprinkler flow. The reasoning is that if this is a fire in building #1, people will likely still be doing dishes, using bathrooms, showers, etc in most of the other buildings. So, that pump is still going to be supplying that demand.
However, NFPA 13R states that you just figure the individual building where you have a combined fireline for the building. My thought is that would be like a single small condo or something where you have the domestic and fire split in the building. This particular project has separate fire lines and domestic water lines to each building.
The main problem on this project is that the sprinkler guy only figured the sprinkler demand for the individual building and used the pump at the left hand side of the curve. There was like 50 psi or so at the street, then boosted with 80 psi @ 500 gpm pump. Well, since the sprinkler demand was so low, he basically had 130 psi to deal with. Now, the AHJ has come back and stated that he wants the domestic load included. The domestic load based on the table in NFPA 13R (A9.6) will be about 400 gpm for this complex. So, they end up losing about 20 psi of total supply pressure. As you can imagine, the system is installed (prior to permits - VERY BAD IDEA) and now none of it works. Due to the very high pressures they thought were available, the lead-ins were installed as 1" pipe, and all 1" and 3/4" cpvc.
So, basically, how would you guys interpret the domestic load that is needed?
Travis Mack
MFP Design, LLC
"Follow" us at
When doing a large apartment complex per NFPA 13R (say 16 buildings where each are appropriate for 13R) that is supplied by a common fire loop, what do you do for the domestic allowance? This particular site had a domestic booster pump placed on the site for the domestic/fire loop. The sprinkler demand is 80 gpm +/- for the 4 residential sprinklers.
Since this is a domestic/fire loop 13R states that you have to figure a domestic allowance. My conservative nature says that you should figure the domestic load for each building on site and include that in the loop with your fire sprinkler flow. The reasoning is that if this is a fire in building #1, people will likely still be doing dishes, using bathrooms, showers, etc in most of the other buildings. So, that pump is still going to be supplying that demand.
However, NFPA 13R states that you just figure the individual building where you have a combined fireline for the building. My thought is that would be like a single small condo or something where you have the domestic and fire split in the building. This particular project has separate fire lines and domestic water lines to each building.
The main problem on this project is that the sprinkler guy only figured the sprinkler demand for the individual building and used the pump at the left hand side of the curve. There was like 50 psi or so at the street, then boosted with 80 psi @ 500 gpm pump. Well, since the sprinkler demand was so low, he basically had 130 psi to deal with. Now, the AHJ has come back and stated that he wants the domestic load included. The domestic load based on the table in NFPA 13R (A9.6) will be about 400 gpm for this complex. So, they end up losing about 20 psi of total supply pressure. As you can imagine, the system is installed (prior to permits - VERY BAD IDEA) and now none of it works. Due to the very high pressures they thought were available, the lead-ins were installed as 1" pipe, and all 1" and 3/4" cpvc.
So, basically, how would you guys interpret the domestic load that is needed?
Travis Mack
MFP Design, LLC
"Follow" us at