Restaurant Plan Review Demand Shortfall and Field Obstruction
Plan review for a 2,400 ft² restaurant tenant in an existing mall shows a wet-pipe system, 12 ft ceiling, light-hazard occupancy, and a hydraulic calculation with a demand of 280 gpm at 58 psi at the base of the riser, including 100 gpm hose allowance. The available city supply at that flow, after private main and backflow losses, is 54 psi. The plans show 1-inch branch lines with eight sprinklers per line, 13 ft spacing, and 7 ft between the deflector and the top of a 5-ft-high partition. The contractor’s field inspection requests approval; you find the installed branch line has been relocated within 4 inches of a 14-inch-deep heating duct, two sprinklers are painted, and the hydraulic placard is missing. The contractor says the duct is “not an obstruction” because it is round.
1. What plan review issues exist, and how should the hydraulic shortfall be handled?
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The demand of 280 gpm at 58 psi exceeds the available 54 psi by 4 psi, so the calculation does not demonstrate adequate supply even before any safety margin. The 100 gpm hose allowance is included, which is appropriate for the calculation, but it does not cure the shortfall. The reviewer should require a revised hydraulic calculation that either reduces the demand, increases the supply, or adds a listed fire pump if justified. The 13 ft spacing and eight sprinklers on a 1-inch branch line may be acceptable for light hazard, but they must be checked against the adopted NFPA 13 pipe schedule and area limitations; they are not the primary issue here. The 7 ft vertical distance between the deflector and the partition top should be evaluated under the obstruction rules, not accepted solely because the partition is 5 ft high. Approval should be withheld until the supply-demand relationship is resolved.
2. How should the field inspection findings affect approval?
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The field installation does not match the approved plans. The branch line relocated within 4 inches of a 14-inch-deep heating duct creates a potential obstruction to spray pattern; the duct being round does not automatically exempt it. The applicable obstruction rules depend on duct width, depth, and distance from the sprinkler, so the contractor must provide a dimensional analysis or relocate the sprinkler. The two painted sprinklers must be replaced because paint can alter thermal response. The missing hydraulic placard is a documentation and maintenance deficiency that must be corrected before final acceptance. The inspector should issue a written discrepancy list, not approve the work verbally. Approval should be conditioned on corrected installation, replacement of painted heads, installation of the placard, and a revised calculation if the field relocation changes the hydraulic demand.
3. What should the contractor submit before the system is accepted?
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The contractor should submit a revised hydraulic calculation showing the actual installed pipe routing and sprinkler locations, with the supply-demand comparison clearly shown. If the duct cannot be relocated, provide an obstruction analysis with dimensions and the proposed corrective measure, such as additional sprinklers or relocation. Submit product data for replacement sprinklers and confirm they match the approved type and temperature rating. Provide a signed statement that the painted heads were replaced and the hydraulic placard was installed. After corrections, the AHJ or inspector should perform a reinspection and witness any required acceptance test, such as main drain, flow switch, and alarm test. The final package should include as-built drawings, the hydraulic placard information, and the inspection report. Approval should not be based on the contractor’s oral assurance that the round duct is acceptable.