EFFECTIVENESS OF WATER TREATMENTS IN PREVENTING CONTAMINATION FROM A
LEADED BRASS
Report No FR0338

Dec 1992

SUMMARY

I BENEFITS

This work provides criteria to determine where the use of leaded copper alloys will not produce unacceptable lead contamination.

II OBJECTIVES

To establish if the water treatments currently used to prevent plumbosolvency will also have a favourable effect on leaded copper alloys and to establish the mechanism of contamination. To determine the effect of galvanic coupling with copper on the contamination level.

III REASONS

Following the publication of British Standard (BS) DD201 , a test method to assess the potential of metallic products to contaminate water supplies, field work was undertaken to investigate the validity of the calibration factor used in the calculation of the final result. This work suggested that the level of contamination might be favourably affected by at least one of the water treatments used to overcome plumbosolvency problems.

IV CONCLUSIONS

  1. Raising the pH of the test solutions produced a significant reduction in lead contamination only under those conditions where theoretical models indicate a significant reduction in the solubility of the lead corrosion product would also occur.

  2. In contrast, under those solution conditions that would either accelerate (high chloride) or inhibit (sulphate to chloride ratio >2) galvanic corrosion, for all but one solution, no significant variation from their respective non-coupled experiments was observed. The exception produced a result contrary to what would be expected if the contamination process was under galvanic control.

  3. The addition of phosphate produced a very large and statistically significant reduction in the contamination under both galvanically coupled and non-coupled situations.

  4. All the evidence suggests that the level of contamination from leaded copper alloys is controlled by the solubility of the corrosion product rather than by any galvanic effect. This implies that any water composition that is satisfactory with lead pipes, either because it is inherently non-plumbosolvent or because it is being treated, will also be satisfactory with leaded copper alloys.

V RECOMMENDATIONS

At the current prescribed value for lead of 50g/L, all the common leaded copper alloys can be accepted for use in contact with those potable waters that have been shown to be satisfactory (i.e. non-plumbosolvent) when in contact with lead pipes.

VI RESUME OF CONTENTS

The report describes a series of laboratory tests on a leaded copper alloy using the DD201 method and a range of waters. In some of the experiments the brass coupons were galvanically coupled to copper foil.

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