Quality & Inspections · Mandatory · Construction

Water and Hydraulic Pressure Test

A record of hydraulic pressure testing on water supply and drainage pipework.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. BS EN 805 / WRAS remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	BS EN 805 + BS EN 806 + Water Supply (Water Fittings) Regulations 1999 (WRAS) + BS EN 13828
Scope	Domestic cold and hot water, LTHW heating, CHW (chilled water), condenser water, and fire suppression systems
Test procedure	Fill with clean water, purge all air, pressurise to 1.5× maximum working pressure, hold for a minimum of 1 hour, acceptable drop typically ≤0.02 bar
Visual inspection	All accessible joints must be visually inspected during and after the hold period for signs of leakage or weeping
Documentation	Completed test record must be retained in the O&M manual as permanent evidence of system integrity at handover

1. Hydraulic Pressure Testing — The Final Check Before Concealment or Commissioning

The hydraulic pressure test is the definitive verification of leak-tightness at a pressure above normal service conditions. It subjects every joint, fitting, valve, and length of pipework to a sustained pressure that exposes defects while they are still accessible for repair. Conducting this test before insulation, burial, or concealment is not optional — it is the last practical opportunity to confirm system integrity.

The test applies across multiple building services systems — domestic cold and hot water, low-temperature hot water (LTHW) heating, chilled water (CHW), condenser water, and in some cases fire suppression. Each system may have different working pressures and therefore different test pressures, but the principle is the same: pressurise to a factor above the maximum working pressure, hold for a defined period, and confirm no loss of pressure and no visible leakage.

The applicable standards — BS EN 805 for water supply, BS EN 806 for installations inside buildings, and BS EN 13828 for heating systems — set out the test parameters, acceptance criteria, and documentation requirements. The completed test record forms a permanent part of the operation and maintenance manual and provides evidence of system integrity at the point of handover.

Retain gauge calibration certificates

Obtain and retain gauge calibration certificates alongside the test record — an uncalibrated gauge makes the test result unverifiable. The calibration certificate must be current at the date of the test and traceable to a national standard.

2. Hydraulic Pressure Test Record Fields

The following table identifies every field that must be captured on a hydraulic pressure test record. Together, these fields provide complete traceability of the test conditions, procedure, and outcome.

Field	Description
Project/system	Project name, building, and specific system or section under test
Date	Date the hydraulic pressure test was conducted
System contents	Medium within the system (clean water, treated water, glycol mix, etc.)
Test medium	Clean potable water — must match specification requirements
Maximum working pressure	The maximum normal operating pressure of the system in bar
Test pressure	Applied test pressure — typically 1.5× maximum working pressure
Test gauge	Gauge type, serial number, range, and calibration certificate reference
System preparation	System filled, air purged from all high points, all joints accessible for inspection
Pressurisation	Method of pressurisation (manual pump, electric pump) and time taken to reach test pressure
Stabilisation period	Time allowed for temperature equalisation and pipe expansion before the formal hold begins
Hold period start	Time and pressure reading at the formal start of the hold period
Hold duration	Duration of the hold — minimum 1 hour per BS EN 806, or as specified
Hold period end	Time and pressure reading at the end of the hold period
Visual inspection	Confirmation that all accessible joints were visually inspected during and after the hold
Result	Pass or fail with pressure drop recorded and any observations noted
Tested by	Name, signature, and qualifications of the person conducting the test
Witnessed by	Name and signature of the witness (client, engineer, or clerk of works)

3. Common Mistakes

Not purging air before pressurising

Trapped air in the system compresses under pressure, giving a false pressure reading and masking small leaks. All high points must be vented and the system must be confirmed full of water before the test pressure is applied.

Not allowing temperature equalisation

If the test water and the pipework are at different temperatures, thermal expansion or contraction during the hold period will cause pressure changes that are unrelated to leakage. A stabilisation period must be allowed before the formal hold begins.

Testing beyond the manufacturer's rated pressure

Components such as valves, flexible connections, and expansion vessels have maximum rated pressures. Applying a test pressure that exceeds these ratings can damage the components. The test pressure must not exceed the lowest-rated component in the system.

Not conducting visual inspection during the hold period

The pressure gauge alone does not tell the full story. A small weeping joint may not cause a measurable pressure drop within the hold period but will cause long-term damage once the system is in service. All accessible joints must be visually inspected during and after the hold.

Testing mixed-service systems as a single test

Systems operating at different working pressures (e.g. domestic cold water at 3 bar and LTHW heating at 1.5 bar) must be tested separately at their respective test pressures. Testing both at the higher pressure risks damaging the lower-rated system.

4. Frequently Asked Questions

What is the test pressure for domestic cold water systems?▾

1.5 times the maximum operating pressure. For a typical domestic cold water system operating at 3 bar, the test pressure is 4.5 bar, held for a minimum of one hour.

What is an acceptable pressure drop during the hold period?▾

Typically no more than 0.02 bar per hour, after temperature stabilisation. Any drop greater than this indicates a leak that must be found and repaired before the system can be accepted.

Does the hydraulic pressure test cover fire suppression systems?▾

No. Fire suppression systems (sprinklers, deluge, gas suppression) are tested to their own specific standards, which set different test pressures, hold times, and acceptance criteria. They must not be included in a general hydraulic pressure test.

When should hydraulic pressure testing occur in the construction programme?▾

Before insulation, burial, concealment, or commissioning. Testing must take place while all joints and fittings are still accessible for visual inspection and repair. Once pipework is concealed, locating a leak becomes disruptive and expensive.

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