Plumbing plumbosolvency

Lead in Drinking Water. The naturally soft, slightly acidic, plumbosolvent water of the Loch Katrine water supply for the Glasgow area was recognized many years ago to release lead from the lead pipes and tanks in the domestic plumbing of the Victorian and subsequent (even post-World War II) eras. ... 

U.S. studies of plumbosolvency in the 1970s and 1980s clearly indicated that there was a high correlation between soft, acidic water and associated lead surface corrosivity and that the overall U.S. picture for contamination frequencies of water by Pb was a variable one. U.S. national household tap water lead surveys (Patterson and O Brien, 1979 U.S. EPA/Levin, 1986 McCabe et al., 1970 Craun and McCabe, 1975) showed (1) one-sixth (16%) of U.S. tap water lead levels were >20 pg/1 (2) 100% of residences with new plumbing with recently soldered connections in copper systems showed Pb s20 pg/1 and that (3) for the sampling year 1988, a total of 42 million U.S. residents had some exposure to water Pb >20pg/l, about 34 million from older housing exposures and 8 million from newly constructed residences (U.S. ATSDR, 1988). 

In compliance modelling for a water supply system, the most important calibration data are (i) the lengths and diameters of the lead service lines (ii) the types (copper, brass, etc), lengths and diameters of premise plumbing (iii) the plumbosolvency of the water and (iv) the percentage of homes with a lead service line in the water supply system. The extent of this data varied in the three case studies necessitating the use of some assumptions, which were adjusted (to a limited extent) in order to match predicted compliance results to those observed. Obtaining adequate calibration data in the future on pipework characteristics should not be particularly onerous or costly, particularly if opportunities to undertake brief inspections of service connections... 

For the two UK case studies, the most important calibration data were the plumbosolvency of the water, the percentage of houses with lead pipes within the water system, and daily water consumptions. Pipe details, water use patterns and flow rates were less critical and general assumptions were often used (Hayes et al, 2006, 2008). For the North American case studies in Cities A, B, and C, the most important calibration data were the plumbosolvency of the water and the length and diameter distributions of the non-lead pipes used in premise plumbing. In these studies the focus of compliance assessment was either sequential 30 minutes or 6 hours stagnation - first draw sampling. For City C, the limited data available for model calibration constrained the scope of the case study. 

Dosing scenarios were then investigated by reducing the values of M and E that define plumbosolvency. As these values were reduced, an equivalent reduction factor was applied to the premise plumbing correction. The results are shown in Table 5.2 for four sequential litre samples, using the plug flow modeL and are compared to the present non-orthophosphate dosed condition. 

If applicable to City C more widely, then the influence of dilution from non-lead premise plumbing extends significantly further than the first litre sample. It is therefore possible that the plumbosolvency of City C s water supplies is significantly higher than is apparent from the synthetic compliance data summarised in Table 7.1. 

This flawed situation is made worse because it will vary, as demonstrated by both the results of the LCR surveys undertaken by utilities (ref City A) and modelling, and it cannot provide any rehable or robust basis for the optimisation of plumbosolvency control. The contribution of lead to drinking water from premise plumbing appeared to be more significant in City A than City C, both of which are in the US, possibly because brass pipes are more common in City A. 

In the optimisation of plumbosolvency control treatment in the three case study Cities, the next step could be to overcome the calibration data limitations that have been identified much of the uncertainties could quickly be reduced by plumbosolvency testing and by obtaining better information on pipe-work circumstances, particularly premise plumbing. Remodelling could then identify optimum treatment conditions with greater confidence. 

Most of the centre of Edinburgh was built in the nineteenth century. Many homes still retain some of their original lead plumbing, and the water is plumbosolvent. Thus water lead makes a substantial contribution to some children s lead intake (Raab et al, 1987). Unlike other inner-city areas, central Edinburgh is more affluent than the rest of the city with a high proportion of owner-occupiers and of people in professional and managerial occupations (SASPAK, 1983). 

From the outset of studies in Glasgow it was clear that potential problems existed with respect to the levels of environmental lead exposure (Goldberg, 1984). Our experience of this suggested that the problem was linked to soft plumbosolvent water supplies and lead plumbing, and consequent increases in blood lead concentration in the general population of the West of Scotland... 

---