Water Systems for Small Communities

A Puzzle Guide for Local Officials
Bulletin 910

Monitoring Drinking Water Distribution to the Customer

Jeff Crisler, Division of Drinking and Groundwater, Ohio Environmental Protection Agency
Karen Mancl, Professor Food, Agricultural and Biological Engineering, The Ohio State University

The quality and quantity of water can change as it moves through a distribution system.

• Water comes in contact with tanks, pipes, fittings, and fixtures.
• Contaminants may be drawn into a water system or even be forced into the system. Leaks, breaks, backflows, and cross-connections all threaten water quality.
• As water is stored in a distribution system the quality degrades with time. Chlorine residuals dissipate; corrosion products, like lead and copper, may increase; and disinfection byproducts may form.
• Breaks and overflows can result in water loss and property damage.

Quantity

A simple yet overlooked aspect of distribution monitoring is rectifying meter readings with the water produced by the system. Differences in what is produced versus what is paid for could be the result of leaks, breaks, overflow, theft, and inaccurate, worn, or missing meters.

Disinfection Byproduct Monitoring

The monitoring program for disinfection byproducts began with the Safe Drinking Water Act of 1974. However, when rules were first adopted in 1979, monitoring was limited to large water systems and only one group of compounds known as THMs. Beginning in 2002 all surface water systems and systems that purchase water from surface water systems must begin monitoring for disinfection byproducts quarterly. Requirements for testing all groundwater systems will begin in 2004.

Since disinfection byproducts form with time and form more rapidly in warm water, the timing and sample location are regulated. For groundwater systems serving less than 10,000 people, samples must be taken when the water is warm and at points in the distribution system where the water is "oldest."

Bacteriological Sample Siting Plan

To ensure that every tap delivers safe water, the distribution system operator must check the quality of water at representative points throughout the system. A plan for checking the distribution system should include:

• Sample locations that are evenly spread throughout the distribution system.
• Instructions on how to properly collect samples.
• Certified laboratories available to run analysis.
• Instructions on response to positive bacteria tests.

Monitoring Program for Lead and Copper

During the mid-1990s all Ohio water systems conducted a lead and copper survey of their service connections. Based on those findings, segments of the distribution system were classified into one of three tiers. This initial survey forms the basis of ongoing monitoring with tier one receiving the most attention.

Monitoring Chlorine Residual

Chlorine is added to finished water to kill pathogens that may enter the distribution system. Chlorine residuals are easy to check as an indicator of contamination. Monitoring chlorine residuals is one of the most important tools available to a distribution system operator.

The goal for chlorine residual is to provide enough chlorine for customer protection (at least 0.2 mg/l free chlorine or 1.0 mg/l combined chlorine) but not too much to cause taste and odor complaints or form excess disinfection byproducts. Chlorine residuals must be monitored in two ways:

1. daily in the distribution system.
2. at the time and place where bacteria samples are collected.