"Gun metal & DZR"
"I am intrested to know what is the limiting factor to use normal brass in the plumbing system of a house for potable water. In other words, what are the threshold values in water (tds, ph, cl, ...) beyond which gun metal or DZR fittings must be used - not normal brass. Also what are the consequences of using brass fittings in the plumbing network where water is aggressive (TDS more than 1200ppm)particularly those related to health?"
We know of no guidelines related to specific limites , tds, pH, Cl, etc. regarding when one needs to use a dezincification resistant brass (DZR) alloy in potable water. Dezincification typically occurs in brass alloys containing more than 15% zinc. Waters that have caused dezincification contained sulfur species, carbon dixoide and oxygen. Stagnant or low velocities waters tend to promote dezincification.
High total dissolved solids (tds) waters are not always aggressive. Aggressive waters can be defined using the Ryzner or Langier indicies, based on the carbonate film-forming capability of a water. One issue related to health vs. the use of brass alloys that we are aware of is a restriction on the use of leaded brasses in potable waters. The EPA has maximum allowable concentrations of lead and arsenic for potable waters.
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