Distribution System Compliance & Best Practices

Water distribution systems are large networks of storage tanks, valves, pumps, and pipes that transport finished water to consumers’ homes and businesses. Due to their design, water distribution systems include areas of vulnerability where contamination can occur.

We have 1188 resources (and counting) on Distribution Systems in our Documents Database that provide valuable information on this topic. You can search for documents about corrosion and corrosion control, calculate the average annual water loss that has affected your system, how to develop and maintain a service line inventory to comply with the Lead and Copper Rule Revisions (LCRR), webinars on distribution system best practices, how to enhance security monitoring for water distribution system facilities that are at risk of intentional contamination, and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Distribution Systems within our database just select "CATEGORY" in the dropdown then choose "Distribution Systems." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.

Disinfection By-Product Control

Disinfection kills or inactivates disease-causing organisms in a water supply. Disinfection by-products (DBPs) are formed when disinfectants used in water treatment plants react with bromide and/or natural organic matter, like decaying vegetation, present in the source water to create harmful compounds. Different disinfectants produce different types or amounts of disinfection byproducts.

We have 829 resources (and counting) on Disinfection and Disinfection By-Products in our Documents Database that provide valuable information on this topic. You can search for documents that explain how to use the Drinking Water State Revolving Fund (DWSRF) to address DBPs in drinking water, the basics of ultraviolet disinfection, disinfectant residual control within the distribution system, webinar recordings on ways to simulate disinfectant water chemistry and ways to assess distribution system influent water quality, and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Disinfection and its potential by-products within our database just select "CATEGORY" in the dropdown then choose "Disinfection and Disinfection By-Products." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.

Optimization Offers "Cushion" to Stay in Compliance

Were you curious to learn more about the "hot topic" issues Dave McMillan discussed in episode 5 of Tap Talk? The Louisiana Department of Health recently organized a 5-hour virtual training as part of their Area-Wide Optimization Program (AWOP) that goes in deep.

According to U.S. EPA, AWOP is "a cost-effective approach to increasing public health protection, proactively achieving regulatory compliance, improving treatment plant performance, and maintaining high water quality throughout the distribution system." In the video, engineer Alicia Martinez describes it more plainly as "going above and beyond so you have cushion when things go wrong." Topics covered in this recording include:

• Naturally Occurring Ammonia
• A Practical Guide to Breakpoint Chlorination
• Chloramine Disinfection Overview
• Interactive Case Studies – Accessing Chloramine Systems
• Dosage Calculations using Davidson Pie Wheel

Please note that this recording is shared for informational purposes only and typically CEUs are not able to be awarded by your certification entity for watching a video recording without specific, prior approval.

Featured Video: Disinfection Byproducts in Tap Water: 5 Things To Know

The challenge of disinfection byproduct (DBP) control in drinking water lies in balancing the varying health risks of over 600 known DBPs with the benefits of microbial waterborne illnesses prevented via disinfection. While DBPs can originate from industrial sources, they generally form in water treatment systems when natural organic matter reacts with a disinfectant, usually chlorine-based. Ongoing studies have suggested that the toxicity for any given DBP can range from having no known health effects to exhibiting links between exposure and cancer, birth defects, or reproductive disorders. Disinfectant type and dose, residual chlorine, inorganic and organic precursor concentrations, pH, temperature, and water age can impact DBP formation.

The management of DBPs in drinking water is enforced through the Stage 1 and Stage 2 Disinfection Byproduct Rule (DBPR). Collectively, the rules set maximum contaminant levels (MCLs) for total trihalomethanes (TTHM), 5 haloacetic acids (HAA5), bromate, chlorite, chlorine/chloramines, chlorine dioxide, and DBP precursors.

According to a 2019 report by the U.S. Environmental Protection Agency (EPA), the Stage 2 DBPR invoked the largest number of community water system violations between 2017 and 2018, accounting for approximately 30% of all drinking water violations. Consecutive water systems, those with surface water sources, and systems serving populations of 501 to 10,000 people experienced violations more frequently. A greater compliance challenge is experienced by consecutive systems because they have little control over the water that they receive. While treated water may have achieved compliance at the system’s interconnection, DBP concentrations can rise through the receiving distribution system.

Non-consecutive utilities experiencing compliance challenges for the Stage 1 or 2 DBPR can start by troubleshooting the system using our previous blog post on The Disinfection By-Product Challenge. Consecutive systems should coordinate with their wholesale system following the approaches suggested in the 2019 report discussed above. The preferable methods of control often lie in prevention and optimization. As your system troubleshoots the cause of high DBP concentrations, keep the community informed on your efforts as well as some basic information on the health effects and sources of DBPs. Operators can find a general overview on DBP challenges in this week’s featured video. We recommend using this video to provide customers with answers to the following questions:

• What are disinfection byproducts?
• How are DBPs regulated?
• How do I know if my water has high levels of DBPs?
• How are people exposed to DBPs?
• How do I remove DBPs from my home’s water?
  
  

Featured Video: What is Water Hammer?

Any water or wastewater operator should possess a strong understanding of water hammer and the implications it can have on piping systems. Water hammer, also referred to as hydraulic shock, occurs when there is a sudden change in flow velocity or direction that results in a momentary increase in pressure. If high enough, the pressure can cause damage to pipes, fittings, and valves. An example where water hammer can occur is when an operator rapidly closes a valve halting flow and sending a shockwave through the system. In Jefferson City, MO, operators responding to a ruptured water main created a second break during repairs as a result of water hammer. Pressure surges can also occur through unexpected power outages or equipment failures.

Engineers consider several variables when designing piping systems to limit potential for water hammer. Whenever a major change is made to the distribution or collection system, implications for water hammer should be evaluated.

This week’s featured video demonstrates how water hammer occurs and what it looks like using 100 feet of clear PVC pipe with an analog and digital pressure gauge. The host explains how engineers can modify the potential for water hammer in piping systems by manipulating the variables that make up the mathematic equation for the pressure profile of a water hammer pulse. Such design parameters include pipe size, recommended operating procures for closing valves, and more. Watch the video to understand how the design considerations for your piping system impact water hammer.

Featured Video: How To: Develop a Cross-Connection Control Plan

A well-developed cross connection control plan ensures that backflow events are an infrequent occurrence in drinking water distribution systems. Cross connections involve any connection between treated water and untreated water. The connection can allow for backflow and ultimately drinking water contamination.  You can learn about the two types of backflow, backpressure and backsiphonage, as well as how they occur in RCAP’s 2018 blog on Cross Connection and Backflow Prevention – Underutilized Protection for Potable Water. Additionally, WaterOperator.org has featured two backflow videos in a previous blog that will help you learn more about the phenomenon.

To prevent unnecessary contamination in your distribution system this week’s blog post features an RCAP video on how to develop a cross connection control plan. This short video describes the key administrative and technical provisions that should be included in your plan. We’ve also highlighted some useful resources that can help you follow their suggestions. If you'd like to find state or territory specific resources such as a sample ordinance or cross connection control plan template, visit our document library 

Now that you know the key provisions to a successful backflow prevention program, check out these additional resources. Remember that many state or tribal territories can have their own rules and specifications that need to be met by your utility. Consults with your system's primacy agency before starting or updating a cross connection control program.

Backflow Prevention – Idaho Rural Water Association
This 2-sided brochure can be used to educate your customers about potential sources of backflow and the impacts of contamination.

Residential Cross-Connection Questionnaire – Alliance of Indiana Rural Water
This 2-page questionnaire can be set to customers to identify potential sources of cross connection.

Selling Cross-Connection Control to Management- University of Florida Center for Training, Research, and Education for Environmental Outcomes
This power point, presented by Ron Chapman, describes how you can encourage your utility to implement a cross connection control program.

Cross-Connection Control Manual – U.S. Environmental Protection Agency
This manual has been designed as a tool for health officials, waterworks personnel, and plumbers to understand the basics about backflow prevention, preventer testing, and control programs.

Featured Video: Water Tower Collapse Compilation

Online trends can seem bizarre, but browsing the web is worth the effort when you stumble upon videos likes these. If you’ve ever searched for distribution maintenance videos on YouTube, you may have already encountered water tower tipping videos. Some of them have reached millions of viewers. Once you watch a few for yourself, you’ll realize why.

There are many reasons a water system might want to remove an existing water tower. Older towers have a higher probability of failing an inspection or causing safety issues to the community. When that happens, it may be easier to just remove the tower provided it’s no longer necessary for the system. If a system has already connected to a newer tower, the costs to maintain redundant towers may drive the incentive for removal. Other times, communities might remove a tower due to damage incurred from a natural disaster or because they want to open the property for other uses.

Only a very small number of tanks are tipped over like the ones in this week’s featured video. Collapsing a tower is a dangerous job only performed in wide open areas with experienced professionals. Generally most tanks are dismantled with a crane instead. Before removal the site may undergo an environmental review. Then if the tower is still in use, it will have to be disconnected from the current water and power supply. After putting out a bid and selecting a contractor, the system will coordinate the rest of the planning with them. Crane dismantling involves cutting the tower into pieces with a torch and lowering those pieces down with a crane. Often times any leftover steel can be sold to a local scrap yard.

So even though tipping a tower is much less common, please enjoy this week’s featured video. It’s hard to look away once you start!

Featured Video: Tech Review: Liquid Flow Velocity

Knowledge of flow velocity, volumetric flow rate, and pipe diameter can assist operators in selecting, installing, and troubleshooting flow meters. This week’s featured video will guide operators in the math used to calculate flow velocity using volumetric flow and or pipe diameter.

Brent Baird with Instruments Direct demonstrates three techniques that will estimate flow velocity. The old school method utilizes a flow calculator slider ruler. With Brent’s particular ruler, by sliding to the known value for the inside pipe diameter (ID) in inches, the velocity in feet per second (FPS) can be read above the known value for volumetric flow in millions of gallons per day (MGD). Alternatively, the inside pipe diameter can be estimated by lining up the known values for velocity and volumetric flow and then looking at the value indicated under pipe diameter. Brent demonstrates that a cross reference chart performs the same calculations using a different visual.

Both of these tools are based off the equation GPM=2.45*ID²*FPS. If neither of his reference tools are available, plugging in the known FPS value for velocity and the inside pipe diameter in inches will calculate the volumetric flow rate. By rearranging the equation to solve for FPS, the flow velocity can be calculated using FPS=GPM/(2.45*ID²). Remember to follow PEMDAS. To calculate the internal pipe diameter with known values for FPS and GPM, rearrange the equation to solve for pipe diameter: ID= √(GPM/FPS/2.45). If the value for the internal pipe diameter is unknown, Brent demonstrates how an ANSI chart can be used to find that value.

With the video's final explanation of basic flow meter requirements, these calculations can be used to spot and avoid problem areas for flow metering in your distribution system.

Testing the Link Between Wildfires and Benzene Contamination

In the weeks following the Santa Rosa, CA wildfires last October, city officials found elevated levels of benzene in water system samples taken from the nearly totally-razed Fountaingrove neighborhood. The first round of samples returned 4 results of over 500 parts per billion, with one of these at 918 parts per billion (MCL for benzene in drinking water is 1 part per billion). A second round of testing produced similar numbers over the MCL, without the higher spikes. A total of 145 samples have now shown elevated levels.

According to this article in The Press Democrat, city officials, who for months have stressed that the contamination appeared isolated to the advisory area, were taken by surprise that six of those results were from outside the existing advisory area.

With the help of a forensic chemist, who helped eliminate the possibility of petroleum leaks, the city now suspects that the most likely cause of contamination is heat damage to high-density polyethylene service lines or other plastic components (such as PVC) in the water or wastewater system. The city is enacting more extensive testing to find out if plastic laterals are responsible. Once the exact cause is identified, the city will consider solutions. Replacing the water system could cost over $20 million.

Interested in finding out more about benzene contamination in drinking water supplies, including sampling methods, treatment strategies, and private well concerns? Check out this EPA website or this Oregon Health Authority factsheet. Another useful resource is this template (from North Carolina) to be used when high levels of Benzene need to be reported to the public.

The Disinfection By-Product Challenge

Staying in compliance with Stage II DBP testing can be a challenge for many small systems. Moreover, when preventing DBP formation becomes a pressing need, it is easy to get overwhelmed by the range and cost of options out there, especially if you are trying to keep up with new technologies. Then there is the fact that solutions to DBP problems often involve several different actions or multiple steps, giving the situation an extra level of challenge.

However, before planning a remediation strategy it might be valuable to initiate a DBP profile study - testing from the source water through the treatment process, and continuing into the distribution system. Why? Because, as Justin Spears in a recent H2Outlook (Kentucky Water & Wastewater Operator's Association) article found out, sometimes the problem isn't where you think it is!

According to his article, he was all set to add a mixer to his storage tank when results from his DBP profile study showed that most of his DBPs were forming in the plant's clearwell. His problem was at the treatment plant, not in the tank! In the end, Justin solved his DBP problem quickly by using chlorine dioxide, made on site by mixing chlorine gas, which he had already in place, with sodium chlorite. However, every treatment plant and source water is different, and what worked for him might not be the best for you.

Interested in finding out more about options for DBP control? Check out this video or this website or this manual. In addition, you can choose Disinfection and Disinfection By-Products as a category in WaterOperator's document or event database to find all sorts of resources.