A hydrostatic pressure test is used to confirm the mechanical integrity of pressure vessels. This comes into play when considering your backyard pool, for example, because there are several types of pressure at work. The water in the pool is exerting pressure against the sides. But the saturated soil around the pool is also exerting pressure. The water flowing through the pool's piping is at pressure, as well. It's important to measure the pressure in all the plumbing of your pool, and this should be done both before the concrete is poured and periodically over the life of the pool.

Tests of this nature ensure that pressured vessels, such as your pool's lines, are free of leaks and strength deficiencies. Some vessels that need hydrostatic pressure testing regularly include residential, commercial, and pool plumbing, pipelines, gas cylinders, and boilers.

It is absolutely crucial to perform these tests correctly and at the right time. The high pressures involved with conducting pressure tests pose safety hazards to those performing the test. With the proper procedural safeguards and precautions, however, it is possible to anticipate potential hazards and avoid or eliminate them. That's why Poolinformer.com has compiled a safety checklist for hydrostatic pressure tests to ensure workers' safety.

When A Hydrostatic Pressure Test Cannot Be Performed

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There are some situations in which it is neither safe nor practical to attempt to perform a pressure test of this type. Most crucially, it is not possible to conduct a hydrostatic pressure test when a vessel requires a pneumatic, or air, test instead. This is the case with some piping systems that have been designed in such a way that they physically cannot be filled with a liquid. There are other piping systems that could potentially accept a liquid, but traces of a liquid would compromise the purity of the lines, such as with piping for the food industry or pharmaceutical manufacturing.

It is also important not to attempt a hydrostatic pressure test on pipes that are known to be compromised. If there have been issues in the past or if visible damage is present, the piping or lines must be replaced or repaired before it is safe to conduct a pressure test.

Testing Hazards

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Knowing in advance what possible hazards could this type of test poses can help keep testers safe. It is crucial to keep an eye out for these possible dangers and ease the hydrostatic pressure test immediately if any are noticed:

  • Flying valves, flanges, gauges and fittings
  • Flying pieces of pipe, pipe fittings, or other fragile system components
  • Oxygen displacement from any inert gases
  • Flooding near energized electric sources

Potential Testing Injuries

The injuries that can be sustained during a hydrostatic pressure test are serious. It is important to understand what they are and prepares for them:

  • Puncture Wounds
  • Eye damage
  • Lacerations
  • Broken bones
  • Contusions
  • Concussions
  • Internal injuries
  • Asphyxiation from leaking inert testing gases such as nitrogen and argon
  • Electrocution from flooding near energized electric sources

Despite these potential dangers, pressure tests are absolutely crucial to establishing that pressure systems are safe, reliable, and free of leaks. Ignoring important pressure tests for the purpose of maintenance can have more catastrophic consequences down the line.

How To Prepare For A Test

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The best way to prevent accidents is to thoroughly and carefully be prepared beforehand. It is crucial that testers follow each of the steps outlined below in the order listed.

Several Days Before The Testing

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  • Check the specification sheet for the applicable vessels. The specification sheets should outline the hydrostatic evaluation pressures, temperature designs, and standards of the vessel.
  • Ensure that supporting documents, such as P&IDs and isometric drawings, are accurate and match the piping to be tested.
  • Develop a test plan and submit it to a supervisor several days before the testing date
  • Confirm that all parties involved in the testing are on the same page regarding procedural safeguards.
  • Inspected all tools, equipment, and piping for damage at least two days before the testing date.
  • Ensure that all equipment and tools to be used in the testing are rated to handle at least 150% of the maximum pressure expected. Use only pressure gauges labeled as "safety gauges" with the "blowout back" feature.

Immediately Prior To Beginning The Test

  • Block off the test location by erecting a safety net around the perimeter. Ensure that only the appropriate personnel remain within the perimeters of the testing area. Erect an appropriate safety warning sign at the test location. It should establish a minimum of a 100-foot perimeter between the testing location and test personnel. The distance of the perimeter may be increased if it is determined that there is the potential for extreme projectiles and/or temperatures.
  • Provide adequate lighting at the testing site for all stages of the testing process.
  • Ensure that vents in the area will adequately vent air and gas. Examine the vent before testing to ensure that it is not blocked.
  • Calibrate pressure management tools and check that the calibration status of the tools is still valid.
  • Lay out all equipment and tools to be used in the testing in such a way as to ensure unobstructed access to the exits in case of an emergency.
  • Drain the vessel's valve at its lowest point to empty completely the vessel, and it's supplying water line.

Test Considerations

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A hydrostatic pressure test will tell you how reliable your vessel is and if it will require any pre- or post-repair or maintenance servicing.  When a storage tank or boiler is involved, the test should be conducted regularly as part of a responsible maintenance program.

Hydrostatic pressure testing of this type should be conducted at least once a year or as often as recommended in your item's schedule of service and maintenance. Tests may be conducted more than once a year if there have been any recent major repairs.

Pressure tests should always be approached with caution. Hydrostatic pressure tests should only be conducted by qualified inspectors who ensure that safety standards are met. The inspector will give you a comprehensive report on your vessel's safety after the test. It is important to note that failing to get the appropriate tests or having them done by unqualified personnel could void any warranty on your pool or other vessels.

Conducting The Test


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When conducting the hydrostatic pressure test, apply a pressure that is 1.5 times greater than the vessel's operating pressure. For example, if the vessel is designed to hold a pressure of 1.0kg/cm2g, the test will need to be conducted at a pressure of 1.5kg/cm2g. To ensure the safety of everyone involved in conducting the test, each step outlined below should be followed in exactly the order listed.

Before The Test


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Ensure that everyone involved in conducting the test has donned the appropriate safety gear and that all required safety gear and supplies are readily available at the testing location. These supplies should include:

  • An emergency spill kit
  • A fire extinguisher
  • Ladders
  • Mobile light plants
  • Whip checks
  • Warning signs and barricades
  • Secured mats and/or ladders to access the applicable vessel

Double check that everyone involved in the test is aware of the correct safety procedures and has the same plan for dealing with any issue that may arise. Then double-check the specification sheet to ensure that the vessel to be tested has not had any previously identified problems. Double-check that the safety relief valve is rated for use at 150% of the anticipated maximum pressure. Finally, double-check the specification sheet to ensure that the standard operating and hydrostatic pressure test pressure of the applicable vessel is accurate.

It is important that the temperature for the water being used in the test be greater than 60 degrees Fahrenheit and that all water hoses be tied down. Then the safety relief valve should be calibrated, and the test can begin.

The Pressurization Process

  • Remove all air from the vessel and the pipeline supplying the vessel through the vent line.
  • Ensure that pressurization is achieved slowly and gradually.
  • Mark all leak points and repair them before proceeding any further with the test
  • Monitor the pressurization points from a safe distance. This can be achieved by looking at the pressurization points from the front of the sight or level glass.

The De-pressurization Process

  • Slowly and gradually open the vent valve to start the depressurization process.
  • To avoid creating a vacuum condition inside the vessel, do not open the drain valve if the vent valve is still closed.
  • Remove all the water completely from the vessel or pipeline supplying the vessel by opening the lowest drain point.
  • Ensure that there is no remaining pressure trapped inside the vessel or the pipeline supplying the vessel before ending the test.


Pressure tests are crucial to the continued safe operation of any vessel under pressure, particularly boilers, pools, and other items on commercial and residential properties. Yet the tests themselves must be conducted carefully to ensure the safety of everyone involved.

Following the checklists both before, during, and after the testing is essential in order to make certain that everyone involved is safe. If proper procedural safeguards for a hydrostatic pressure test are not followed, those conducting the tests can suffer serious injuries or even be killed. Hydrostatic pressure tests should always be conducted by certified inspectors and on vessels in good operating condition. If done carefully, pressure tests of this type are safe to conduct and ensure that the vessel being tested will work properly for a long time to come.

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