Test pressure is normally 30% higher than the design pressure

Test pressure is normally 10% higher than the design pressure

Recommended for high pressure applications

Recommended only for low pressure applications

Test media (Water) used is not compressible by pressure application

Test media (Air) used is compressible by pressure application

Energy stored per unit volume of water under test pressure is very negligible

Energy stored per unit volume of compressed air under test pressure is very high

Needs thorough cleaning after test to

eliminate moisture especially for service which are reactive to moisture / fluids

Easy to clean after testing

Pressure Relief devices are recommended to control sudden increase in pressure during testing

Pressure relief devices are must during test to ensure no over pressurisation

Chances of equipment/ Pipe / test apparatus

failures are very low

Chances of equipment/ Pipe / test apparatus

failures are high

Weight of equipment along with test medium as

water is high hence special attention should be given to floor and supporting arrangements

Weight of equipment with test medium

as air is comparatively less

Needs verification and examination of joints and connections before testing

Needs very careful checking of weld joints thoroughly before testing

Test media can be reused or transferred to other place after testing

Test media can not be reused or transferred to other place after testing

Skilled and semi skilled personnel can carry out the test

Needs involvement of senior experienced staff to monitor the test.

Recommended where large volumes are to be tested at same time (example pipe lines )

If pipe lines are tested should be done with small segmental lengths at a time.

Damages made by failures are less compared to failures in pneumatic testing

Damages made by failures in testing are very huge and extensive

Hydrotest is a regular day to day practice and safe procedure and it can be followed in any work site

Needs special attention and safety precautions

 Pressure changes finite amount by infinitesimal change in volume

 Pressure change proportional to volume change