Streamline - Spring 2014 - (Page 29)

Establishing a Water Distribution System Flushing Program THERE ARE MANY reasons why a lot of water systems do not actively pursue a flushing program. Some of the most common reasons are: * "We don't have the time or manpower to devote to it." * "It would be an inefficient use of water." * "We wouldn't know where to begin." Your system can maintain a fresher water supply by implementing the use of a flushing program, and therefore provide a better finished product to your customers. The list is essentially endless, but the fact remains that an efficient flushing program is an integral part of water distribution system operations and maintenance. Not unlike your vehicle, your water distribution system requires regularly scheduled maintenance in order to perform under optimum conditions. Every water treatment plant operator is more than familiar with system sampling requirements and their frequency. In addition to an up-todate sampling and analysis program, your water system should ideally also have an up-to-date ongoing flushing program as well. The purpose of a regular flushing program is to remove or flush out minerals; sediment, discoloration and other particulate organic matter than can accumulate in the water distribution lines over the course of time. After all, even the best water can become stale if not used or turned over regularly. Your system can maintain a fresher water supply by implementing the use of a flushing program, and therefore provide a better finished product to your customers. A fresher water supply will allow for the use of a reduced amount of disinfectant, such as chlorine, in the water, but still maintain an adequate disinfection amount as required by regulatory agencies. Just because they carry potable water does not necessarily mean that the interior of water pipes are clean. Water mains are designed to carry fire flow, which usually is several times in volume more than domestic or commercial flow rates. As such, during normal residential usage, the flow velocity through the pipes is normally fairly low. Because of this, solids may settle out on the bottom of the pipes, becoming a more significant problem where there are dead-end lines not looped into the system or in areas of low-water use. Over time, these deposits can reduce the carrying capacity of the pipe and result in complaints of discoloration and taste/odor problems when stirred up by increases in flow. A good flushing program utilizing high velocity will normally remove most of the settled substances and discolored or stale water. Preventive maintenance of the water system will also allow personnel to check, record and update water pressure and flow rates in order to ensure the water system is functioning properly and to verify that there is ample water flow for firefighting suppression. Identification of hydrants, valves, and other appurtenances in need of repair or replacement can then be prioritized and worked into a systematic repair schedule. To break it down, flushing involves opening specifically selected fire hydrants and valves under controlled conditions to scour the inner surface of the pipe wall. A desired velocity of at least 2.5 feet per second should result in an acceptable scour effect. The scouring process helps to remove corrosions, scale, and sediment that accumulate naturally over time. If otherwise left in place, these deposits can degrade water quality and restrict pipeline carrying capacity, resulting in a decrease of available volume and pressure. In the time leading up to the beginning of the flushing program, all water reserves should be gradually increased in order to compensate for the demand of water that will be used in the 29

Table of Contents for the Digital Edition of Streamline - Spring 2014

From the President
From the Executive Director
The Importance of an Immediate Response
What’s New in UV?
Proper Disposal of Pharmacy Products
Source Water Protection Notes
Ergs, Joules and Other Stuff
Establishing a Water Distribution System Flushing Program
Wastewater Math
Curtis Water Wins Big in D.C.
Throwing My Loop: Friends to Keep You Warm
eLearning Benefits
Membership Application
Do You Know What Your VRWA Benefits Are?
VRWA Mailbag
Welcome New Members
Training Calendar
Board of Directors
VRWA Committees
Index to Advertisers/

Streamline - Spring 2014