29 CFR 1910 · General Industry · Subpart L

1910.159(c): Automatic Sprinkler System Requirements

By Black Belt Safety Editorial Team Official text as of octubre 15, 2026 Data updated octubre 23, 2026 5 min read

In plain words:

Employers must make sure automatic sprinkler systems are designed for complete coverage, use only approved equipment, and are properly maintained. A main drain flow test is required on each system annually, the inspector's test valve must be opened at least every two years, and systems need acceptance tests and a reliable water supply.

Key takeaways

  • 1910.159(c) is part of OSHA's general industry standards (29 CFR Part 1910, Subpart L).
  • OSHA cited it 71 times in the last 3 years, in 71 inspections, with $172,673 in current penalties.
  • Most citations: NC (10), NV (10), PR (9).
  • Related part: 1910.159(c)(10) Sprinkler spacing (55 citations).
  • Free 5-minute toolbox talk for your crew below.
71citations, 3 years
$172,673current penalties
71inspections
0linked injury cases
In this article
  1. What this rule covers
  2. Official text
  3. Where and how often it was cited
  4. Free toolbox talk
  5. OSHA interpretation letters
  6. Related parts of this rule
  7. Get your crew competent
  8. Frequently asked questions
  9. About this page

What this rule covers

29 CFR 1910.159(c) ("General requirements") is one requirement inside 1910.159 Automatic sprinkler systems, an OSHA general industry standard (Part 1910, Subpart L). It includes 21 sub-paragraphs. The official text below is copied word for word from the Electronic Code of Federal Regulations (eCFR). The numbers, injury cases and training on this page show how OSHA enforces it on real job sites.

Official text

(c) General requirements — 71 citations

(1) Design. 2 citations

(i) All automatic sprinkler designs used to comply with this standard shall provide the necessary discharge patterns, densities, and water flow characteristics for complete coverage in a particular workplace or zoned subdivision of the workplace. 2 citations

(ii) The employer shall assure that only approved equipment and devices are used in the design and installation of automatic sprinkler systems used to comply with this standard.

(2) Maintenance. The employer shall properly maintain an automatic sprinkler system installed to comply with this section. The employer shall assure that a main drain flow test is performed on each system annually. The inspector's test valve shall be opened at least every two years to assure that the sprinkler system operates properly. Open (c)(2) 11 citations

(3) Acceptance tests. The employer shall conduct proper acceptance tests on sprinkler systems installed for employee protection after January 1, 1981, and record the dates of such tests. Proper acceptance tests include the following:

(i) Flushing of underground connections;

(ii) Hydrostatic tests of piping in system;

(iii) Air tests in dry-pipe systems;

(iv) Dry-pipe valve operation; and

(v) Test of drainage facilities.

(4) Water supplies. The employer shall assure that every automatic sprinkler system is provided with at least one automatic water supply capable of providing design water flow for at least 30 minutes. An auxiliary water supply or equivalent protection shall be provided when the automatic water supply is out of service, except for systems of 20 or fewer sprinklers.

(5) Hose connections for fire fighting use. The employer may attach hose connections for fire fighting use to wet pipe sprinkler systems provided that the water supply satisfies the combined design demand for sprinklers and standpipes.

(6) Protection of piping. The employer shall assure that automatic sprinkler system piping is protected against freezing and exterior surface corrosion. 1 citations

(7) Drainage. The employer shall assure that all dry sprinkler pipes and fittings are installed so that the system may be totally drained.

(8) Sprinklers. 1 citations

(i) The employer shall assure that only approved sprinklers are used on systems.

(ii) The employer may not use older style sprinklers to replace standard sprinklers without a complete engineering review of the altered part of the system.

(iii) The employer shall assure that sprinklers are protected from mechanical damage. 1 citations

(9) Sprinkler alarms. On all sprinkler systems having more than twenty (20) sprinklers, the employer shall assure that a local waterflow alarm is provided which sounds an audible signal on the premises upon water flow through the system equal to the flow from a single sprinkler. 1 citations

(10) Sprinkler spacing. The employer shall assure that sprinklers are spaced to provide a maximum protection area per sprinkler, a minimum of interference to the discharge pattern by building or structural members or building contents and suitable sensitivity to possible fire hazards. The minimum vertical clearance between sprinklers and material below shall be 18 inches (45.7 cm). Open (c)(10) 55 citations

(11) Hydraulically designed systems. The employer shall assure that hydraulically designed automatic sprinkler systems or portions thereof are identified and that the location, number of sprinklers in the hydraulically designed section, and the basis of the design is indicated. Central records may be used in lieu of signs at sprinkler valves provided the records are available for inspection and copying by the Assistant Secretary.

[45 FR 60710, Sept. 12, 1980; 46 FR 24557, May 1, 1981]

Source: eCFR, text current as of 2026-10-15. Read all of 1910.159.

Where and how often it was cited

YearCitations
20235
202426
202521
202619

Top states: NC (10), NV (10), PR (9), OR (8), NY (7)

Largest penalties

EmployerLocationPenalty for this rule
KRAFT HEINZMUSCATINE, IA$110,000
MURDOCH'S RANCH & HOME SUPPLYCHEYENNE, WY$8,649
HOBBY LOBBY STORES, INC.QUEENSBURY, NY$7,093
AVAMERE AT RIO RANCHORIO RANCHO, NM$6,953
HALE PRODUCTS, INC.OCALA, FL$4,766

Free toolbox talk

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OSHA interpretation letters

Related parts of this rule

Get your crew competent

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Frequently asked questions

How often is a main drain flow test required?

The employer must make sure a main drain flow test is performed on each system annually.

How often must the inspector's test valve be opened?

At least every two years, to make sure the sprinkler system operates properly.

How long must the water supply last?

Every automatic sprinkler system needs at least one automatic water supply able to provide design water flow for at least 30 minutes.

About this page

Sources

3-year window. Federal OSHA only; state-plan rules are not counted. Plain-language text is a summary, not legal advice; the official text controls. Black Belt Safety is not part of OSHA or the Department of Labor.

Written and reviewed by

Black Belt Safety Editorial Team

Site Safety Officer and Safety Professional

OSHA 30 · CPR · USACE CQM

Written and reviewed by the Black Belt Safety team. Every post is checked against the OSHA standard or agency source it cites.

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