After the completion of an installation, it is essential that all piping system be inspected and tested hydraulically to consider the safety and efficiency of the system, except that pipes for gases may be tested pneumatically. if the installation is large one, it may be tested in section of suitable length.
Before the commencement of any testing, the system should be visually inspected to ensure that the recommendation for the correct installation procedure have bean complied with, and that the pipe line together with the appliances, vales and fittings are supported in the prescribed manner.
Whilst the testing pressure may vary depending upon the type and duty of the system, this should normally be 1½ times the max working pressure at the point of max stress.
Pressure should be applied either by a manually operated hand pump or by a power driven pump. Pressure gauges should be correctly positioned and closely observed to ensure that at no time is the test pressure exceeded. the system should be slowly and carefully filled with water, care being taken to avoid all surging pressure of water hammer. Air vents should be open at all high point so that air may be expelled from the system during filling.
When the system has been fully charged with water and all air displaced from the line, air vents should be closed and the line initially inspected for seepage at joints and a firmness of support under load. Pressure may then be applied until the required test level is obtained.
With the test pump stops, the required pressure should be maintained without loss for a period of 1 hr, or for such shorter time as agreed between supplier and purchaser. any defect revealed by such tests should be made good and the test repeated until a satisfactory result is obtain.
A further test should be made of the entire system at normal service operating pressure. Valves and appliances should be tested for ease of operation and correct working.
Buried pipes should be tested before back filling is completed. Where pipe line contain couplings which permit the pipe to slip, it is essential that consideration be given to restraint of the line before pressure is applied. Partial back filling, leaving joints expose for inspection, is usually found to be satisfactory, although for some high pressure applications additional bracing particularly at changes of direction may be found necessary.
In special cases where hydraulic tests are not practical, pneumatic tests may be substituted, but this should not be attempted without consultation with the supplier of the pipe.
Pumping mains should be subjected to a test pressure at least 1½ times the line pressure, with a maximum pressure as agreed with the pipe manufacturer.