A PIRB CoC is a self-certification and declaration by the PIRB licensed plumber that the work undertaken by them is up to standard and professionally conducted as per their training.
Subject to the requirements for issuing a PIRB CoC, a PIRB CoC must be issued on all plumbing work undertaken by a Licenced plumber which includes but is not limited to geysers, solar water installations, heat pumps, etc.
To who do I  
issue  
a COC?
Each Plumbing Certificate of Compliance comes in a triplicate form with the top copy to be given to the owner, the 2nd copy to given to local authorities, municipalities and/or insurance if relevant and the last copy to be kept in a secure place by the licensed plumber as part of their administration process