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Hydrostatic Testing

Hydrostatic Testing always includes both an internal and external visual examination of the cylinder.

Hydrostatic testing is conducted by using water or other non-compressible fluid as the test medium.

Examination of Cylinder Condition

Where a fire extinguisher cylinder or shell has one or more of the following conditions, it shall not be hydrostatically tested, but rather will be condemned or destroyed by your Triangle Fire technician:

  • Where repairs by soldering, welding, brazing, or use of patching compounds exist.
  • Where the cylinder threads are worn, corroded, broken, cracked, or nicked.
  • Where there is corrosion that has caused pitting, including pitting under a removable nameplate or nameband assembly
  • Where the fire extinguisher has been burned in a fire.
  • Where a calcium chloride type of extinguisher agent was used in a stainless steel fire extinguisher.
  • Where the shell is of copper or brass construction joined by soft solder or rivets.
  • Exceeds 1/4 in. (0.6 cm) if the dent includes a weld.
  • Where the depth of a dent exceeds 1/10 of the greatest dimension of the dent if not in a weld, or exceeds 1/4 in. (0.6 cm) if the dent includes a weld.
  • Where any local or general corrosion, cuts, gouges, or dings have removed more than 10 percent of the minimum cylinder wall thickness
  • Where a fire extinguisher has been used for any purpose other than that of a fire extinguisher
  • When a fire extinguisher cylinder, shell, or cartridge fails a hydrostatic pressure test, or fails to pass a visual examination as specified in 5-1.4, it shall be condemned or destroyed by your Triangle Fire technician.

*A condemned cylinder can not be repaired.

hydrostatic testing

The hydrostatic retest shall be conducted within the calendar year of the specified test interval.


A hydrostatic test is performed on fire extinguisher hose assemblies equipped with a shutoff nozzle at the end of the hose. All valves, internal parts, and hose assemblies are removed and the fire extinguisher emptied before testing.

The pressure in a hydrostatic test of a cylinder is maintained for a minimum of 30 seconds, but for no less time than is required for complete expansion of the cylinder and to complete the visual examination of the cylinder.

A permanent record shall be maintained for each cylinder tested.

High Pressure Cylinders and Cartridges:

Cylinders or cartridges that pass the hydrostatic test shall be stamped with the technician's identification number and month and year of the retest per TC/DOT requirements.

Hose Assemblies:

Hose assemblies that pass a hydrostatic test do not require recording, labeling, or making.

Low-Pressure Cylinders:

Fire extinguisher cylinders of the low-pressure type that pass a pressure hydrostatic test shall have the information recorded on a suitable metallic label or equally durable material affixed by means of a heatless process.