No, each installation should have its own CoC issued. In terms of issuing a PIRB CoC on installation, the PIRB’s defines an “installation” as any plumbing works that is downstream of any installed water-meter. For example, in the case of a complex or group of houses, it is a legal requirement that each unit or house in a complex or group of houses must be individually metered with a water-meter. As such, each unit or house constitutes an installation and a CoC must be written out for every unit/house.