Wet-Pipe Internal Inspection and Main Drain Deterioration
A 10-year-old wet-pipe system protects a six-story office building. Annual inspection reports are complete, but the owner cannot produce records of any internal pipe inspection. During this year's main drain test, the static pressure is 70 psi and the residual is 52 psi; last year's residual was 61 psi at the same static pressure. The inspector's test connection discharges rusty water for about 30 seconds before it clears. The building has 6-inch steel mains and 2-inch branch lines. The owner wants to defer any further investigation until the next annual inspection because the system has never had a false alarm or failure. The fire official is reviewing the ITM program after a tenant complaint.
1. What inspection, testing, and maintenance deficiencies exist under NFPA 25?
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Two deficiencies stand out. First, NFPA 25 requires an internal inspection of wet-pipe piping at 5-year intervals; a 10-year-old system with no records is overdue. Second, the main drain test has deteriorated from 61 psi residual to 52 psi at the same 70 psi static, about a 15% drop, which exceeds the common 10% investigation threshold and indicates a possible restriction or underground/main condition. Rusty discharge at the inspector's test is also a sign of corrosion or obstruction and should trigger an obstruction investigation, not just flushing.
2. What actions should the owner and contractor take, and can the investigation be deferred?
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The owner cannot defer. The contractor should perform an obstruction investigation, internal inspection at representative locations including the 6-inch main and branch lines, and flow tests, then clean or replace affected pipe. The main drain test should be repeated and compared with the baseline. If the internal inspection finds significant tuberculation or debris, the system should be flushed and a corrosion assessment performed. The fire official should require a written ITM report and a correction schedule; closing the control valve or draining the system without an impairment program is also a violation.