Abstract: A suitable casting alloy for use in a fluid treatment device may be made as a copper-nickel-zinc-tin (CU--NI--ZN--SN) alloy without the addition of silver, silicon or magnesium, if certain identified trace metals are kept below certain levels. It appears that the previously identified additive metals, which are either expensive or dangerous, act to counteract the deleterious effects of these trace contaminants, and are not necessary of the contaminants are controlled. A method of forming the alloy prevents the explosive reactions encountered when melting together metals having significantly differing vaporization and melting temperatures.