How is a hydrostatic test performed?

A hydrostatic test is also commonly known as a leak test. This test is conducted to check the durability and leaks of various piping systems, boilers, gas cylinders, and other pressure-containing things. Unlike many other testing methods, the hydrostatic method does not harm the products. That’s perhaps the most standout feature of this test. At the same time, you have to be on top of your preparation while performing the hydrostatic test; otherwise the outcome could go against you. You have to tick a lot of boxes to perform this test without leaving any loopholes.

How is a hydrostatic test performed

Here is how you can conduct a hydrostatic test successfully:

  1. Design

A hydrostatic test begins with design. Everything is mapped out in the designing phase. For example, if the workers are posed with a problem during the hydrostatic test, they must have, most probably, discussed that problem during the design part. So it will not take much to sail through the issue.

Following factors are chiefly considered while crafting the design:

  • Size and length of the pipe
  • Making changes in the high spots
  • The demand for flow/volume

Make sure your design strictly follows the specifications mentioned in AWWA M41 manual and AWAA C600 Standard.

  1. General requirements

The hydrostatic testing is a complicated process and therefore comes up with a lot of general requirements. After completing the designing, the next step is to tick all the requirements:

  • Before putting all the high-pressure piping in the hydrostatic test, they should be checked with water
  • Irrespective of the size, all the connections should be installed before the pressure testing
  • Ball and gate valves should be tested in the half-open position
  • DPS (Department of Public Safety) should be informed 48 hours before you discharge hydrostatic test water

This is just a small list of some essential requirements. However, you could be obliged to do more.



  1. Safety measurements

First thing first. Your staff should be trained. By training, I don’t mean to say those who have learned things through word-of-mouth but those who have a proper academic background in this particular field.

Also, have a look at the following safety requirements:

  • Always use authorized equipment
  • Nobody should be associated with the testing process outside the testing area
  • If the hydrostatic test takes place in the night, you must install proper lighting
  • During the testing process, no personnel should tight the screwed fitting. The pressure should be stopped before doing so
  • The corporation responsible for the test must work in the collaboration of NYSDOT

Again, there could be more measures you could be entitled to take. But that’s the minimum you will have to do.

How is a hydrostatic test performed - testing

  1. Multiple methods of hydrostatic test

There are three prominent hydrostatic methods to test small pressure cylinders and vessels. They are as follows:

  1. Direct expansion method: In this method, the vessel or cylinder is filled with a specific quantity of water. Henceforth, the system is pressurized, and the amount of water is measured after the pressure is released.
  2. Water jacket method: This method involves filling a vessel with water and then being loaded it into a sealed chamber which also contains water. Afterward, the pressure is applied to a vessel inside the test jacket for a defined period. This results in the expansion of the vessel. Finally, the total expansion is measured, and the vessel is depressurized to bring the vessel in its original size and form.
  • Proof pressure method: This test is applied to determine whether or not the vessel contains any leak, wall thinning, or other faults which might become problematic at some point.
  1. Dewatering

Once you are done with the test, here comes the dewatering process. It should be done with utmost care. Otherwise, all your hard work can go down the drain.

  • Soon after the test is over, you should dewater the pipeline applying pipeline pigging process
  • The hydro test water should be disposed of in an appropriate manner
  • Until the pressure is entirely over, the mainline should not be attached to the discharged pipe
  1. Cleaning and drying

The final step of the hydro test is cleaning and drying. Here is how it is done:

  • The organization involved in the testing process should bring to -30°F inside the pipeline. Until this dewpoint is achieved, the pipeline will not be considered clean
  • As soon as the drying and cleaning process is over, the pipeline should be rooted out and loaded at the earliest

Final thoughts

As you can see, a great deal of preparation, hard work, and thought go with the hydro test. Even tiny misconduct can cause a lot of damage. Therefore, one has to be careful right from the word goes. However, this blog can serve you like the blueprint to conduct a hydro test with ease.


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1 thought on “How is a hydrostatic test performed?”

  1. Victoria Addington

    I chose to learn more about hydrostatic testing because my uncle has been talking about it and I’m not familiar with it. It’s good that you said that the purpose of this test is to examine the resilience and leakage of different types of piping systems, boilers, gas cylinders, and other items that are subjected to pressure. I’m grateful you shared this! Hiring a professional to handle it sounds like a smart idea because it appears a bit complex. I’ll make sure to let him know about this and look into services that can be helpful.

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