The complete unit may include automatic devices, by-pass valves, flow-restrictors, etc., provided that each test circuit between the meters to be verified and the control tanks is clearly defined and that it is possible to check the internal pressure tightness of the circuits at any time.
Any type of water supply system may be used, but if several test circuits are operated in parallel, there must be no interaction incompatible with the requirements of 5.2.3.
