Which table gives the hanger spacing?
NFPA 13-2025 gives the maximum distance between hangers by pipe material and nominal size in Table 17.4.2.1(a) (ft-in) and Table 17.4.2.1(b) (m) (17.4.2.1). The two tables are printed separately: the calculator reads the ft-in table in US units and the metric table in SI. Sizes marked NA (not applicable) cannot be chosen; for example ¾ in steel pipe, threaded lightwall steel 3½ in and larger, and CPVC 3½ in and larger are not in the table.
- Steel (except threaded lightwall): 1–1¼ in 12 ft-0 in; 1½–8 in 15 ft-0 in.
- Threaded lightwall steel: 1–3 in 12 ft-0 in.
- Copper tube: ¾–1 in 8 ft-0 in; 1¼–1½ in 10 ft-0 in; 2–3 in 12 ft-0 in; 3½–8 in 15 ft-0 in.
- CPVC: from 5 ft-6 in at ¾ in to 10 ft-0 in at 3 in; for listed nonmetallic pipe the spacing is modified as the product listing specifies (17.4.2.2).
- Ductile iron: 15 ft-0 in for 3, 4, 6 and 8 in.
End sprinkler and armover
For steel pipe, the unsupported horizontal length between the end sprinkler and the last hanger must not exceed 36 in (900 mm) for 1 in pipe, 48 in (1200 mm) for 1¼ in and 60 in (1500 mm) for 1½ in and larger (17.4.3.4.1); for copper tube 18 / 24 / 30 in (17.4.3.4.2). Where the limit is exceeded, the pipe is extended beyond the end sprinkler and supported by an additional hanger (17.4.3.4.3). The cumulative unsupported armover is limited to 24 in (600 mm) for steel and 12 in (300 mm) for copper (17.4.3.5.1). These rules cover steel pipe and copper tube only (17.4.3.1).
Pendent sprinklers above 100 psi
Where the maximum static or flowing pressure at the sprinkler (other than through the fire department connection) exceeds 100 psi (6.9 bar) and a branch line above a ceiling supplies pendent sprinklers below it, the end length drops to 12 in (300 mm) for steel and 6 in (150 mm) for copper (17.4.3.4.4.2), and the armover is limited to the same values (17.4.3.5.2.1). The hanger supporting the pipe to the end pendent sprinkler must restrain upward movement (17.4.3.4.4.1).
Number of hangers and rod size
The calculator limits every span from the cross main connection to the maximum table spacing and puts the last hanger no farther from the end sprinkler than the allowed end length: N = ⌈(L − e) / S⌉. There must be at least one hanger for each section of pipe (17.4.3.2.1); starter lengths under 6 ft (1.8 m) do not need a hanger (17.4.3.2.4). Rod size comes from Table 17.2.1.1: 3/8 in (10 mm) up to 4 in pipe, 1/2 in (13 mm) for 5–8 in.
Load rule
Engineer-certified hangers are designed to support five times the weight of the water-filled pipe plus 250 lb (115 kg) at each point of support (17.1.2(1)). For steel pipe, the water-filled weight is taken from NFPA 13 Table A.18.5.9 (Schedule 40 and Schedule 10), and the calculator takes the pipe length per hanger as the maximum spacing. Example: 4 in Schedule 40 pipe weighs 16.40 lb/ft; at 15 ft spacing 5 × 16.40 × 15 + 250 = 1480 lb.
Frequently Asked Questions
What is the hanger spacing for steel sprinkler pipe?
Per NFPA 13-2025 Table 17.4.2.1(a), steel pipe other than threaded lightwall: 12 ft-0 in for 1 and 1¼ in, 15 ft-0 in for 1½ in and larger. ¾ in steel pipe is NA (not applicable) in the table.
How far can the end sprinkler be from the last hanger?
For steel pipe 36 in for 1 in, 48 in for 1¼ in and 60 in for 1½ in and larger (17.4.3.4.1); for copper 18 / 24 / 30 in (17.4.3.4.2). Above 100 psi with a branch line above a ceiling feeding pendent sprinklers below, 12 in for steel and 6 in for copper (17.4.3.4.4.2).
Why is CPVC spacing different?
Table 17.4.2.1 gives CPVC from 5 ft-6 in at ¾ in to 10 ft-0 in at 3 in; for listed nonmetallic pipe the spacing is modified as the product listing specifies (17.4.2.2). The end and armover rules in 17.4.3 cover steel and copper only.
What load is a hanger designed for?
Engineer-certified hangers support five times the weight of the water-filled pipe plus 250 lb (115 kg) at each point of support (17.1.2(1)). Water-filled steel pipe weights are in NFPA 13 Table A.18.5.9; for example 4 in Schedule 40 pipe weighs 16.40 lb/ft.
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