The subject of brass v copper is out of hand, I suggest they read Model Boilers & Boilermaking  by K.N.Harris.
My problem. I have designed a small boiler, which I presented to the club (Southern Federation affiliated) tester. Yes the calculation seam O.K. but he would not test it if I built it as it was not an approved design. I also have 2 published plans 1 by E. T. Westbury & 1 by W.Melville as on working pressure is stated on either they are not approved ether

Which are the "approved designs" and who makes that decision? And which country, by the way.

It seams it is up to the tester, if they don't feel qualified. Off course this is the U.K. where all rules apply. All I want is a certificate for insurance. Approved designs are published designs? but they must have a working pressure stated, or they must be recalculated. My design was for below 1.5 bar-liter now the Nov 2008 edition states only boilers over 3.0 bar-liter need regular test, below this rules do not apply. How ever an initial test is required by the club insurance, so I can opperate in a public area.

Thanks!