Full Description

The Seattle School Board adopted a policy in 2004 that limits acceptable lead (Pb) levels to 10g/L at drinking water sources in Seattle public schools. Several possible sources of Pb wereidentified in school piping systems including brass components and fittings in end-use plumbing.Field and laboratory studies were therefore conducted to determine Pb release from new end-useplumbing components and fittings installed at drinking water sources (primarily fountains) inSeattle Public Schools. Field studies were conducted by collecting sequential small-volumesamples at 16 sources in 3 schools to assess the relative contributions of the various end-usecomponents and fittings to lead in drinking water at the tap. Results indicated that most of thelead contained in first-draw 250-mL samples originated in the first 50 mL drawn from thesource. Laboratory studies utilized stagnation and flow-through testing procedures on new end-usecomponents and fittings with local tap water to determine Pb release as a function ofcumulative contact time. Laboratory results showed elevated Pb levels during early testing,followed by a general decline in Pb levels with repeated exposures attributed to passivation ofexposed brass surfaces. Periodic spikes in Pb observed for some components (i.e., bubbler headsand brass shutoff valves) were attributed to the movement of the valves during sample collectionand possible release of machining residuals and metal particulates, or dezincification of brassmaterials. Field and laboratory testing results are significant because new end-use plumbingcomponents typically had been installed in Seattle Public Schools immediately after purchase,without pre-conditioning. Results from this study were used to help identify likely causes of highPb levels in water samples and develop mitigation measures, such as pre-conditioning of end-useplumbing components, so that drinking water sources can be used immediately after beingretrofitted with new components and fittings in Seattle Public Schools. Includes 8 references, table, figures.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 19File Size: 1 file , 520 KB