DE Fire Sprinkler cheat sheet

Light hazard: design density 0.10 gpm/ft² over 1,500 ft²; Ordinary Hazard Group 1: 0.15 gpm/ft² over 1,500 ft²; OH2: 0.20 gpm/ft² over 1,500 ft²; OH3: 0.30 gpm/ft² over 1,500 ft²; EH1: 0.40 gpm/ft² over 2,500 ft²; EH2: 0.50 gpm/ft² over 2,500 ft² (NFPA 13 density/area curves).

Maximum coverage area per sprinkler: light hazard 225 ft² (ordinary 130 ft², extra hazard 100 ft²) for standard spray upright/pendent; extended-coverage sprinklers permit larger areas per listing.

Maximum spacing between standard spray sprinklers: 15 ft for light hazard, 15 ft for ordinary, 12 ft for extra hazard; minimum spacing 6 ft unless baffles or listed for closer spacing.

Maximum distance from sprinkler to wall: one-half the allowable spacing (e.g., 7 ft 6 in for light hazard at 15 ft spacing); maximum distance to wall for extended-coverage per listing.

Sprinkler deflector distance below ceiling: 1 in to 12 in for standard spray; 1 in to 18 in for extended-coverage; listed for 1 in to 6 in for concealed spaces.

Branch line and cross main layout: branch lines spaced ≤ maximum sprinkler spacing; cross mains sized by hydraulic calculation; use remote area shape (rectangular or 1.2√A per NFPA 13) to determine number of sprinklers flowing.

Quick-response sprinklers may use reduced design area (e.g., 30% reduction for wet systems with ≤ 1,000 sq ft remote area, subject to ceiling height limits) per NFPA 13 area reduction rules.

Residential sprinklers: design per NFPA 13R/13D; minimum density 0.05–0.10 gpm/ft² depending on number of heads; maximum coverage 400 ft² per sprinkler for 13D with 12 ft spacing.

NFPA 13 governs commercial sprinkler design/installation; NFPA 13R for residential up to 4 stories; NFPA 13D for one- and two-family dwellings and manufactured homes.

Hanger spacing: steel pipe 1 in and smaller ≤ 12 ft; 1¼ in and larger ≤ 15 ft; CPVC and copper per listing (typically 10–12 ft); hangers within 3 ft of a sprinkler and 6 ft of a change in direction.

Pipe schedule method allowed only for certain sizes/hazards; hydraulic calculation is required for most new systems; use C-factors: steel 120, cement-lined 140, copper 150, CPVC 150.

Underground mains: minimum 6 in for fire service unless hydraulic calculations justify smaller; gate valves on supply lines; thrust blocks at changes of direction.

Sprinkler escutcheons required where pipe penetrates ceiling; sprinklers must be accessible for maintenance; no painting of sprinklers except per listing.

Spare sprinkler cabinet: stock at least 6 spare sprinklers (or 2% of total, whichever is greater) of each type/ temperature rating; wrench provided.

Control valve supervision: all control valves must be supervised open (tamper switch) or locked; main drain and flow test connections required at system riser.

Acceptance test: hydrostatic test at 200 psi for 2 hours (or 50 psi above working pressure if >150 psi); flushing per NFPA 13; flow test to verify water supply.

Hazen-Williams formula: P = 4.52 Q^1.85 / (C^1.85 d^4.87) where P is friction loss per foot (psi/ft), Q in gpm, d inside diameter in inches, C roughness coefficient.

Flow test: static pressure, residual pressure, and flow rate; plot on semi-log paper; available pressure at sprinkler demand flow = static − (static − residual) × (Q_demand / Q_test)^1.85.

NPSH not applicable to fire pumps; ensure suction pressure ≥ 0 psig at 150% of rated flow; churn pressure ≤ 140% of rated pressure for centrifugal pumps.

Safety margin: 10 psi or 5% (whichever is greater) between supply and demand at the base of the riser; include hose allowance (100 gpm light, 250 gpm ordinary, 500 gpm extra hazard).

Remote area calculation includes: sprinkler discharge (density × area), pipe friction, elevation changes (0.433 psi/ft), fittings (equivalent length), and hose stream allowance.

Backflow preventer and meter losses must be included; use manufacturer curves; add 10 psi for dry pipe/ preaction system air pressure if applicable.

Pump curve: rated flow at rated pressure; shutoff pressure ≤ 140% of rated; select pump so demand point is on the right side of the curve (not beyond 150% flow).

Velocity in sprinkler piping should not exceed 20 ft/s for supply mains and 10–15 ft/s for branch lines to limit friction and noise.

Weekly: check control valves open, gauges normal, pump status; monthly: test alarm devices, check waterflow switches, inspect dry pipe air pressure.

Quarterly: test main drain (flow test), check waterflow alarm, inspect gauges; annual: full flow test, dry pipe valve trip test, fire pump flow test, backflow preventer test.

Main drain test: record static and residual pressure; a drop of more than 10% from previous test may indicate supply obstruction; compare to baseline.

Dry pipe valve trip test: annually with system air pressure; record time to trip and time for water to reach test valve; ensure < 60 seconds for water delivery.

Fire pump annual flow test: at churn, 100%, 150% of rated flow; compare to baseline; test results kept on site; weekly no-flow (churn) run for diesel pumps.

Sprinkler spare head inventory: verify at least 6 spare sprinklers of each type and temperature rating; replace any painted, corroded, or damaged sprinklers.

Gauge calibration: replace or calibrate gauges every 5 years; test alarm and supervisory circuits per NFPA 72; record all ITM in logbook.

Impairment procedures: notify fire department and insurance carrier; establish fire watch; use NFPA 25 impairment handling; restore system promptly.

Delaware adopts NFPA 13, 13R, 13D, and NFPA 25 through the Delaware State Fire Prevention Regulations; local amendments may apply in Wilmington and New Castle County.

Sprinkler contractor licensing: Delaware requires a business license and a certified sprinkler fitter/ contractor; verify with Delaware Division of Fire Prevention.

Plan review and permits: submit construction documents to Delaware Office of State Fire Marshal or local authority having jurisdiction (AHJ) before installation; fees based on project scope.

Delaware workers' compensation insurance required for employees; general liability and completed operations coverage typically required for sprinkler contractors.

Contract requirements: written contract must include scope, code edition, warranty, and payment terms; Delaware Home Improvement Commission rules apply to residential work.

Recordkeeping: retain design calculations, test results, and ITM records for at least the life of the system; provide owner with O&M manuals and as-built drawings.

Delaware fire code enforcement: annual inspection of sprinkler systems required for commercial occupancies; AHJ may require more frequent testing for high-hazard occupancies.

Lien rights: Delaware mechanics' lien for labor/materials; file within 90 days of last work; preliminary notice not required for subcontractors but recommended.