Public Water Supply Distribution Systems Assessing and Reducing Risks: First Report (2005) / Chapter Skim
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3 Highest Priority Issues
3 Highest Priority Issues
Pages 10-18
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From page 10... ...
based on a series of expert and stakeholder workshops from 2000 to 2003. The nine white papers focused on the following events or conditions that can bring about water quality degradation in public water supply distribution systems: 1.
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From page 11... ...
However, the committee decided to follow the structure of the EPA white papers in preparing this report, with the recognition that overlaps and difficult-to-separate phenomena exist. Of the issues presented in the nine white papers, cross connections and backflow, new or repaired water mains, and finished water storage facilities were judged by the committee to be of the highest importance based on their associated potential health risks.
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From page 12... ...
Regulatory options that could be considered include requiring inspections for household cross connections at the time of home sale. Furthermore, training programs such as those offered by the New England Water Works Association to train and certify backflow device installers and testers have been successful in gaining support from the plumbing community and in developing local plumbing codes that require cross connection control.
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From page 13... ...
Furthermore, periodic changes to the operation of the distribution system, such as valving the local water system to shut down mains for work and then reloading the mains before their return to use, can allow for contamination of the drinking water supply from backflow through unprotected domestic and fire connection services, which is covered under the section on cross connections and backflow. Craun and Calderon (2001)
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From page 14... ...
One of the most important manifestations of water quality degradation during water storage is a loss of disinfectant residual, which can be further compromised by temperature increases in water storage facilities under warm weather conditions. Internal chemical contamination can also occur due to leaching from coatings used in the storage facility, or solvents, adhesives, and other chemicals used to fabricate or repair floating covers.
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From page 15... ...
While water quantity objectives promote excessive storage, water quality objectives are geared toward minimizing residence times and frequent exercising of treated water facilities to maximize the stored water disinfectant residual. Appropriate balancing is therefore required to ensure disinfection effectiveness and sufficient level of service (Boulos et al., 1996; Hannoun and Boulos, 1997)
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From page 16... ...
The problems of greatest concern within premise plumbing include microbial regrowth, leaching, permeation, infiltration, cross connections, leaks and the resulting indoor mold growth, scaling, and the high costs of failure. Regrowth problems are exacerbated in premise plumbing due to very long stagnation times resulting in a loss of chlorine residual, to the presence of numerous microclimates, and to nutrient release from some pipes.
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From page 17... ...
The premise plumbing issue poses unique challenges because there is no obvious single party who could assume responsibility for the problem, which might be best addressed through changes in and enforcement of plumbing codes, third party standards, and public education. Utility involvement in overseeing solutions may be appropriate where distribution system water quality directly contributes to the problem, as is currently the case with the Lead and Copper Rule.
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From page 18... ...
Finally, with an increase in the importance of security of drinking water pipes, pumps, reservoirs, and hydrants, there is a corresponding increase in the responsibility of operators to make decisions during perceived security events.
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