Welcome to the forum. Although you can post in any forum, the USA forum is here in case of local regs or laws
To be classed as competent, you need to be G3 registered.You only need to be competent to install but registered to register its all straight forward
I am, have been for years just seems a waste of money paying for cps when I might only do 1 or 2 a year
Reply to the thread, titled "notifying unvented cylinder" which is posted in UK Plumbers Forums on Plumbers Forums.
We recommend City Plumbing Supplies, BES, and Plumbing Superstore for all plumbing supplies.