Sprinkler System Maintenance Guide: NFPA 13 and NFPA 25 Compliance

System types you may be maintaining

Wet pipe systems

The most common type. Pipes are filled with water under pressure, ready to discharge through any sprinkler that opens. Used in heated spaces where freezing is not a concern.

Dry pipe systems

Pipes are filled with pressurised air or nitrogen. When a sprinkler opens, the air bleeds out, the dry pipe valve trips, and water enters the system. Used in unheated spaces and freezers.

Pre-action systems

A two-step system that requires both a fire detection signal and a sprinkler activation before water flows. Used in spaces where accidental discharge would be costly — data centres, libraries, museums.

Deluge systems

All sprinklers are open at all times. Water is held back at a deluge valve and flows everywhere when the valve opens on a fire signal. Used for high-hazard environments such as fuel storage and aircraft hangars.

Core components subject to inspection

• Sprinkler heads (pendent, upright, sidewall, concealed, ESFR — each rated to a specific temperature and orifice).
• Branch lines, mains, and risers.
• Control valves (OS&Y or butterfly) with electric tamper switches.
• Alarm check valve, dry pipe valve, pre-action valve, or deluge valve depending on system type.
• Waterflow alarm switch and pressure switches connected to the fire alarm panel.
• Inspector test valve at the most remote point of the system.
• Backflow preventer where required by local code.
• Antifreeze loops for areas exposed to low temperatures.

NFPA 25 maintenance frequencies

Weekly

• Visual inspection of dry pipe valve enclosures and any heated valve rooms.
• Verify control valves on dry, pre-action, and deluge systems.

Monthly

• Check gauges on wet pipe systems for normal pressure.
• Inspect electric tamper switches and confirm they signal a closed valve to the panel.
• Visual check of all control valves to confirm they are open and locked, sealed, or supervised.

Quarterly

• Test the waterflow alarm at the inspector test connection — water should flow within 90 seconds and the alarm should sound at the panel.
• Test supervisory valve, low-air, and high-water signals.
• Inspect hydraulic nameplate, hangers, and bracing.

Annually

• Internal inspection of alarm and check valves.
• Trip test of dry pipe and pre-action valves.
• Main drain test on every system riser to verify the supply.
• Inspection of every accessible sprinkler head, hanger, brace, pipe, and fitting.
• Antifreeze loop test of solution concentration and freezing point.

Every 5 years

• Internal pipe inspection at strategic points to check for obstruction, corrosion, microbiologically influenced corrosion (MIC), and scale.
• Gauges replaced or recalibrated.

Every 50 years (and based on type)

• Standard response sprinkler heads must be sample-tested at 50 years; quick-response heads at 20 years; high-temperature heads at 5 years.
• Dry sprinklers must be tested or replaced at 10 years.

Common findings during inspections

• Closed control valves — the single most common deficiency. Even a partial closure reduces flow.
• Painted sprinkler heads. Once paint coats a sprinkler, the response time element is compromised and the head must be replaced.
• Corroded pipes in concealed spaces, especially in dry pipe systems where residual water sits in low points.
• Obstructed sprinkler heads from stored stock, ductwork, signage, or new partitions installed below the head.
• Missing spare sprinkler heads. NFPA 13 requires a stocked spare sprinkler cabinet with a wrench and at least 6 sprinklers of each type and temperature rating.
• Hanger and brace failures from corrosion, vibration, or seismic events.
• Hydraulic nameplate missing or unreadable — inspectors will ask for it.

Best practices

• Tag every control valve with its supervised position and link it to a tamper switch.
• Photograph all gauge readings and store with the inspection report so trends are visible over time.
• Maintain the spare sprinkler cabinet next to the riser and check it during every inspection.
• Walk the entire system after any tenant fit-out or ceiling change to confirm coverage has not been disturbed.
• Schedule the 5-year internal pipe inspection ahead of the deadline — internal corrosion is a slow killer of dry pipe systems.