Abstract

Brasses used in potable water distribution systems had up to 8% lead until January 2014. Thereafter, the 2011 Federal Reduction of Lead in Drinking Water Act came into force to protect the public from lead exposure, requiring new brass alloys that do not exceed a surface-weighted average of 0.25% Pb, and which are termed “nonleaded”. Many nonleaded brass products are now available, but their propensity to fail as a result of erosion corrosion is unknown This study tested the performance of commercially available nonleaded brass elbows (C46500) in a recirculating Cross-linked Polyethylene (also called, PEX) rectangular pipe loop by exposing to hard water with high concentrations of suspended aragonite particulates that form at high temperature and conditions on the surface of heating elements. Fully penetrating leaks occurred in the elbows in an alarming 13.5 days at 13 ft/s (4 m/s) and 50-55°C at pH 7.5, whereas an identical condition without particles remained undamaged. Further investigation showed erosion corrosion can be severely accelerated dependent on pH, flow velocity, particle size, and type of disinfectants present. This is the first study to demonstrate that nonleaded brass fittings (C46500) are especially vulnerable to rapid failures due to erosion corrosion.

Introduction

Used as an engineering alloy for over a millennium, brasses (typically copper-zinc alloys with other trace metal elements) are widely used for intricate components in drinking water distribution systems. The plumbing devices with critical brass components include pipes, plumbing fittings, valves, heat exchanger tubes, water meters, backflow preventers, bearings, and pump impellers. These copper alloys are preferred for such applications because of their “good strength and ductility …combined with excellent corrosion resistance and superb machinability.”¹ In general, the service life of these components is expected to be at least 20 years, and more commonly 50 to even 100 years performance can be achieved.

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