Inspection process
Hydrostatic test
Also called: hydro test, hydrostatic pressure test, pressure test
A hydrostatic test fills a piping system, tank, or vessel with water and raises the pressure to a specified level for a set period to confirm it holds. Used on plumbing, fire sprinkler mains, and process piping, it proves the joints, fittings, and material are sound before the system is concealed or put into service. Water is used because it's nearly incompressible, so a failure leaks rather than releasing stored energy the way a gas test can.
Why it matters
A leak found in a hydrostatic test is a fitting to remake; the same leak found after the walls close, the system is charged, and the building is occupied is water damage and a demolition bill. The test is a hold point precisely because it has to pass before the piping gets buried, backfilled, or covered.
How it shows up on site
The system is isolated, filled, bled of air, and brought to test pressure, then watched for pressure drop and visible leakage over the required hold time. Plumbing piping is tested to the plumbing code's requirements and fire sprinkler piping to the fire protection standard; the test result is recorded before any pre-cover or backfill step can close.
Standards it's verified against
Checklists that put hydrostatic test to work
Free, field-ready checklists, each with the photo every item needs before it can be submitted.
Related terms
- Rough-in inspectionVerification of concealed MEP work — piping, wiring, and ductwork in the framing — before insulation and finishes cover it.
- Pre-cover inspectionThe last inspection of an assembly before it is concealed — drywall, insulation, backfill, or a slab pour that hides the work underneath.
- Hold pointA stop in the inspection and test plan where work cannot continue until a required party inspects and signs off the release.
- Witness pointA step where a party is invited to observe the work, but the crew may proceed if that party doesn't attend within the agreed notice.
- Definable feature of workA discrete, separately inspectable task or segment of work with its own start, finish, and acceptance criteria within the QC plan.
- Preparatory phase inspectionThe first of the three phases of control — a before-work review of submittals, materials, and criteria for a definable feature of work.
Knowing the term is step one. Proving it is the job.
RTI holds the submit button until every mandatory item is answered and the photos are attached, then chains the record so it can be proven untouched later.