The commissioning sequence and what the specified soundness test establishes about tightness.
Commissioning in order
Commissioning brings a cold water system into safe use in a logical order:
- Inspect the installation against the drawings and specification.
- Flush out debris.
- Carry out the specified soundness or pressure test and assess tightness under those test conditions.
- Disinfect where required, then flush through.
- Fill, set and balance controls such as pressure-reducing valves, and check flow rates.
- Label, record results and hand over.
The soundness test
The soundness test checks tightness under the defined test conditions. Judge the pressure behaviour and any visible leakage against the procedure for the installed materials. BS EN 806-4 sets out test procedures; the principle is to fill, vent the air, raise the system to the specified test pressure, which is commonly related to the maximum design pressure, and hold it while watching for a pressure drop or visible leaks. Plastic pipe expands a little under pressure, so the standard gives a procedure that allows for this rather than a single simple hold.
A note on method
Water is normally used for the test. High-pressure air testing stores a great deal of energy and is hazardous, so it is avoided or used only with appropriate precautions.
Always confirm the exact test pressures, durations and procedure against BS EN 806-4 and BS 8558 for the materials installed.
The test the Regulations set
The Water Fittings Regulations require every system to withstand at least 1½ times the maximum pressure it is designed to operate at; that figure is the test pressure. A system designed for a maximum of 4 bar, for example, is tested at 6 bar.
- No plastics pipe: pump the whole system to the test pressure, then continue for one hour without further pumping. The pressure must hold for that hour, with no visible leakage. This zero-loss requirement belongs to the stated no-plastics test; the plastic tests below have different criteria.
- Plastics pipe, Test A: pump to the test pressure for 30 minutes, then reduce the pressure to one third of the test pressure. Over the next 90 minutes it must not fall below that third, with no visible leakage.
- Plastics pipe, Test B: pump to the test pressure for 30 minutes and note the pressure, then continue for 150 minutes without pumping. The drop must be less than 0.6 bar over the following 30 minutes, or less than 0.8 bar over the following 150 minutes, with no visible leakage.
Every system must be tested, flushed and, where necessary, disinfected before it is first used.
Between testing and occupation
A wet pressure test leaves the system needing water-quality management until it enters regular use. Draining it leaves damp surfaces and trapped pockets that can still support biofilm. If occupation is delayed, follow a documented hygiene plan, including the required flushing and checks. Plan the final commissioning work close to use and confirm any special requirements for components kept out of service.