Distribution system flushing programs have been around for a long, long time. In a nutshell, these programs provide systems with an organized way to clean out the rust and other sediments that have settled in the water lines over the years. Whether water system crews simply crack open a few fire hydrants around town or have spent a great deal of time devising an in-depth unidirectional flushing program (UFP), it’s a sure bet that if your system hasn’t been flushed for awhile your water quality will suffer. If this is the case, then there is no time like the present to take a closer look at your distribution system’s preventative maintenance program before you receive a phone call like:.
Caller: Hi, this is Mrs. Johnson over on Highland Street. I noticed this morning when Howard, you know, my husband, was getting dressed that his socks had a strange orangeish color. It’s really kind of embarrassing, but when I first noticed it, I accused him of sneaking off from work to go golfing again.
Water System Employee: Golfing? What does that have to do with us?
Caller: Well, last time he went golfing he ended up retrieving at least three golf balls from the large pond over on the golf course. Since his slice is really bad…I guess he had to wade way out into the pond before he could find the balls he’d lost. When he got home that night his clothes smelled like dead frogs and they had the same kind of orangeish color.
Water System Employee: I see. I’m afraid that we can’t help Howard with his golf game.
Caller: I doubt that anybody can. But, you see…Howard swears that he wasn’t golfing yesterday and he really didn’t smell like dead frogs this morning…Is there anyway that the water in our washing machine could have turned his socks orange?
Water System Employee: Well… I guess it is possible…We haven’t flushed the water lines in your neighborhood for several years.
Caller: Oh!…Is there anything you can do about it? You see…the kids were a nightmare yesterday and I’m afraid that I got just a little upset at Howard when I thought he’d snuck off to the golf course…Now his face has also turned a strange shade of orangeish-red and I’m not sure what to do about that color either.
Distribution system flushing should be a regularly scheduled maintenance task for every system no matter how big or small. In fact, many experts recommend that systems should be flushed twice a year to maintain consistent flow and pressure and the highest quality water.
Flushing is generally performed by isolating sections of your distribution system and opening flushing valves, or more commonly fire hydrants, to cause a large volume of water to pass through the isolated pipeline and flush it clean.
Consider the fact that even if your system just so happens to produce the finest, purest water in the entire world…if you are pumping it through a pipe that is full of sediment and rust…your customers will never realize the benefit of all your hard work.
While we probably can’t help you improve your golf game, this issue of the Safe Drinking Water Trust eBulletin will help you improve the efficiency and quality of your distribution system, keep your valves and hydrants in top shape, and may even keep you, and a few of your customers, out of hot water.
Additional Resources
http://www.nesc.wvu.edu/ndwc/articles/OT/WI04/valve.html [1]
The Royal Flush
The distribution system is a key element of every water utility. In fact, it is so important that most systems spend roughly 60 to 70 percent of their capital investments on getting treated water to their customers. Remember, your responsibility doesn’t end the moment that the water leaves your treatment plant. You are also responsible for delivering a safe and reliable supply of water all the way to the customer’s tap.
A good flushing program will help you do just that. It should also serve as the cornerstone of your distribution system’s preventative maintenance program. There are basically three flushing methods utilized by water systems today:
Unidirectional Flushing: A method of cleaning water lines by directing the flow of water in one direction within the system to a selected hydrant flushing point. In this type of flushing program, valves are closed in a specific sequence to create water movement in one direction while opening specific hydrants at the end of that sequence to allow the debris to “flush” from the system. The flushing sequence should be designed to begin at the source and work from the inside out forcing water from clean to dirty pipes and from larger to smaller mains. This type of flushing program generally requires up to 40 percent less water than other flushing programs.
Conventional Flushing: Generally the most common flushing program used by smaller water systems since it requires less planning and can be quickly implemented. Conventional flushing programs consist of opening hydrants in a specific area of the distribution system until preselected water-quality criteria are achieved (flush until the water coming from the hydrant appears clear).
Continuous Blowoff: Commonly selected by systems that have a large number of dead-ends and continuous water-circulation problems. Continuous blowoff, or bleeding, of water lines is conducted to force a low velocity-flow of water through a small portion of the system. This process can be set up to operate automatically.
While research shows that a unidirectional flushing program offers the most efficient way to clear your distribution system of unwanted sediment and debris, it is clearly the most complex and time-consuming program and may not be possible for your system to implement in the near future. Therefore, it may be a good idea for your system to implement a conventional program as a more immediate solution while you begin the planning process for a unidirectional program.
Additional Resources
http://emengineers.com/Newsletters/fall_2001_newsletter.htm [2]
To Flush, Or Not to Flush: That is the Question!
In order to get your system’s flushing program off the ground it is a good idea to begin the process by taking these four simple steps:
Step 1—Determine if you need a flushing program: If your utility has water-quality issues that can be assessed by either customer complaints and/or by direct sampling, or you are having difficulties maintaining a disinfectant residual in portions of your distribution system, then it is time to implement a flushing program.
Step 2—Planning and managing a flushing program: Developing a good flushing program requires planning, lots of planning. However, if proper attention is given to the planning stage, the field work required to actually accomplish the program can be greatly reduced. In this stage of the game, your flushing crew will need to gain a thorough understanding of how their system works. If your system has access to hydraulic models of your distribution system, then this is the time to locate them. If not, then an accurate map of your distribution system will be required so that your utility won’t run the risk of shutting off critical customers at inopportune times, resulting in phone calls that you probably don’t want to have to deal with.
Tip: Be sure to check out this month’s Management At a Glance section of the Safe Drinking Water Trust eBulletin to learn how to calculate velocity.
Step 3—Implementing the program: Once your flushing plan has been laid out using your system maps and/or hydraulic models, the next step is to make certain that the valves that you will be using to create dead ends are in working order. This is a good test of how well your system has been at maintaining its valve exercise program.
Once your crews are ready to start flushing, a number of issues will need to be addressed such as:
• Determining flushing velocity requirements.
• Developing standard operating procedures.
• Addressing public and employee safety concerns.
• Meeting all public notification requirements.
• Collecting and maintaining all relevant data for evaluation.
Step 4—Evaluation and revisions: Once you have finished flushing your distribution system, an evaluation should be conducted to determine just how effective your program has been. The evaluation stage should include an assessment of costs so that your system can establish a cost/benefit analysis of the program. Once the evaluation process is complete, your system should have a clear picture of how to make your flushing program an even greater success the next time around.
Following the Flush—Close the Lid!
A routine flushing program is a good overall maintenance program to have in place. Not only does it allow you to do a little “spring cleaning” of your distribution system, it provides immediate improvements to your water quality, helps you meet increased regulatory requirements, gives you an opportunity to exercise your valves, and can help improve the taste of the product you deliver to your friends and neighbors—as well as yourself. Plus, it never hurts when the public gets an opportunity to see your crews hard at work—ensuring the quality of the water they drink.