What is a Hydrostatic Pressure Test?

According to the Occupational Safety and Health Administration (OSHA), “Hydrostatic testing is the method used to pressure test … critical components for leaks and structural flaws by pressurizing them with a liquid.” A hydrostatic pressure test is a method of testing fire extinguisher canisters and fire suppression system plumbing like pipes, tanks, boilers, and tanks for strength and to discover any leaks, which may reveal themselves only under pressure.


A hydrostatic pressure test involves filling the vessel or system to be tested with water under pressure. Sometimes, the water in the system will be dyed a bright color to make any leaking liquid more pronounced visually when it does actually leave the system. The system’s pressure readiness is measured by how much pressure is lost after the system is pressurized to a specific PSI (pounds per square inch), and its strength is measured by any permanent deformation done to the vessel under pressure.

Hydrostatic pressure tests may be required by law to be performed at regular intervals to ensure safe up-to-date operation of the system when it is needed. These tests are performed to identify and correct any defects or degraded materials that make up the system when exposed to a normal or above-normal operating pressure.


Most cities in the United States have laws or building codes that require pressure vessels like fire extinguishers to be tested regularly, for example every two years (with a visual inspection annually) for high-pressure gas cylinders and every five or ten years for low-pressure ones such as fire extinguishers. Gas cylinders which fail are normally destroyed as part of the testing protocol to avoid them being reused. These common gas cylinders have the following requirements:

  • DOT-3AL gas cylinders must be tested every 5 years and have an unlimited life.
  • DOT-3HT gas cylinders must be tested every 3 years and have a 24-year life.
  • DOT-3AA gas cylinders must be tested every 5 years and have an unlimited life. (Unless stamped with a star (*) in which case the cylinder meets certain specifications and can have a 10-year hydrostatic test life).

Typically organizations such as ISO, ASTM and ASME specify the guidelines for the different types of pressure vessels.

Fire Sprinkler Testing

All State Sprinkler Corp. performs five-year hydrostatic pressure tests on a daily basis with New York City Fire Department personnel. Our testing crews work on sprinkler and standpipe systems – supplied by gravity tanks, pressure tanks, or street-level city water supplies.The scheduling of these tests is handled directly with the fire department’s appointment desk.

Five-year hydrostatic pressure tests are life-saving procedures. These tests simulate actual fire department operations that take place during a fire. All State performs these tests as accurately and diligently to assure you that your sprinkler system will always be fire ready.

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