Water Distribution

By Jadorian Paul

Water distribution deserves a great amount of attention in cities. The UN has estimated that as much as 50 percent of the water used in cities is wasted in leaks.¹ Some of the most prominent sources of leakage include “toilet flappers, dripping faucets, and other leaking valves.”² Such waste unnecessarily strains our water provisions, limiting the available water supplies that can be distributed among millions of individuals.¹ Thus, finding ways to improve the movement of water into and through cities is an important step to increase a city’s water supply. Inefficient water distribution is a problem that plagues many cities around the world regardless of economic standing or political influence, because they neglect to acknowledge the importance of their water distribution systems for increasing water efficiency.³ In order to improve a city’s water distribution and maximize efficiency, three major courses of action should be taken:

1. The optimization of piping within building units,
2. More widespread utilization of water towers,
3. The incorporation of SCADA (Supervisory Control And Data Acquisition) technology.

These actions would strengthen the water distribution network, minimizing water and energy waste while also maintaining practicality and flexibility for the system.

Household Piping

To maximize the water efficiency of the internal hot water system of a building, two major things should be kept in mind: length and diameter of the piping. First of all, the length of the pipes in the system should be optimized to successfully accomplish the purpose of moving the water through the household while minimizing the length of the piping.^4,5 One way to do this is to place the water heater in a “central location relative to the fixtures.”⁵ “Plumbing areas” such as  bathrooms and kitchens, placed near one another reduce the area span by hot water piping.⁴ The length of the piping is important for efficiency because longer pipes hold more water. This can be problematic when it comes to hot water delivery. Some water will leave a fixture, only partially heated, and will go down the drain unused before hot water is able to come out.⁵ This water is wasted, as is the energy used to heat it. The goal is to reduce the amount of water that can be stored in the piping between a fixture and a hot water source.

The diameter of the piping should also be taken into account.^4,5 In many cases the diameter of hot water pipes can be optimized to achieve acceptable flow rates and water velocity. Gary Klein, managing partner of Affiliated International Management, states that house pipes are often much larger than necessary in order to maintain “adequate system pressure.” Simply put, they make it much easier to meet required system pressure requirements. By using the smallest possible diameter which achieves the necessary requirements, efficiency can be aggrandized, because less water will be held throughout the pipes after the water is turned off in a building.⁵

Water Towers

The installation of water towers is the best way to improve the movement of water throughout the city. Water towers are useful for the balance they strike between flexibility and energy efficiency. In this system, pumps are used to fill tall-standing towers and water flows through pipes to houses.⁶ One of the major benefits of water towers is the fact that they are still able to run during an event such as a power outage because after the water is pumped up into the tower, the release of water and subsequent energy production relies on gravity rather than pumps.⁶ Water held in the tower will travel down the pipes towards houses whether the pumps are functioning or not. In addition, the energy used to pump the water to the towers is partially recovered from gravity when the water falls down through pipes toward the houses as shown in Figure 1. This makes the system more flexible when it comes to unforeseen disasters because it can still function, even when issues, like pump malfunctions, occur. Andrew Boyd, who has a Ph.D. in operations research, states that water towers may have decreased energy demand as a result of their ability to use smaller pumps to accomplish the same task. Rather than using large pumps to keep up with times of the day with high demand, water towers store water refilling during times of low usage, such as at night. This makes it easier to keep up with demand and allows for smaller pumps to suffice in achieving the same result.

Figure 1. Water tower system. Source: “The Landscape of the City Upon a Hill” blog by Greg Giles

One example of the use of water towers can be seen in Macon, Georgia. Macon constructed a water tower for over $600,000, a sum that they will be able to regain after 20 years as a result of the new water tower.⁷

Water towers may vary widely on type based on the size or design of the one being bought, but the price tends to fall around a million dollars regardless of the design.⁷ This is a large sum of money and smaller cities may not be able to afford it. Such cities would either have to look towards grants and donations from private or governmental sources, or would have to save money over a period of time. Either way, water towers allow for greater flexibility in the water distribution system and should, because of this, be highly considered.

One drawback to these towers is that they must be taller than the buildings that they are supplying water to; water must have a sufficient amount of energy to reach a particular point in the target area. There is also significant energy loss due to friction in the piping, which decreases the efficiency of the system as the length of the piping increases.⁸ One possible solution would be to use more pumps to propel the water so that the water towers do not have to be as high. The problem with this is that it would make the system more vulnerable if there were a pump failure and would thus restrain the overall flexibility.

Maintenance and Control

Constant repairs and maintenance of the piping to reduce leaks contribute to the optimization of the distribution of water within cities. The best way to do this is to make use of smart water technologies which aim to reduce the amount of water that is unintentionally lost. “Incorporating smart water technologies allows water providers to minimize non-revenue water (NRW) by finding leaks quickly and even predictively using real-time SCADA (Supervisory Control and Data Acquisition) data and comparing that to model network simulations,” according to an article by Mark Leinmiller, a manager at Schneider Electric, and Melissa O’Mara, a chief catalyst at Schneider Electric.³ The SCADA would include the use of data collection devices and software that would allow a much better understanding of the condition of the water distribution system.⁹ In addition, such technology would allow different systems to work together and to benefit one another. For example, models of stormwater overflow can be used by different municipal departments, such as the transportation department, to adjust a system in anticipation of a problem such as flooding.³

One study tested the abilities of SCADA technology by using it on Vijayawada, a city in Andhra Pradesh, India.¹⁰ Researchers utilized equipment such as flow meters, chlorine analyzers, and Intelligent Electronic Devices to monitor reservoirs throughout the city. As a result of the experiment, chlorination optimization was improved, demand management was successfully implemented and multiple other benefits were experienced.¹⁰

The most prominent drawback of this system is the money and labor required to make it happen. Though the SCADA software is free, it is currently estimated that about $100,000 is needed for “the installation of SCADA monitoring.”¹¹ This may seem like a very large sum, but it pales in comparison to the amount that would be saved through the use of this technology. It is estimated that households waste over 10,000 gallons of water per year, which is over $90 of water.² In addition, about half of a city’s water is lost to leakage annually.¹ SCADA would help to locate leaks, whether in a household or outside of houses. The value of the lost water eventually surpasses the cost of the SCADA installation after several  years, because with hundreds or thousands of households within a city each losing about $90 of water annually, a city loses at least $9,000 a year just from its households and not including the loss of water outside the household. Despite this, many countries may not have enough funds to push for this development.  However, Leinmiller and O’Mara point towards one option, which is to “[leverage] energy-saving performance contracts.” These contracts form an agreement with the private sector that ensures private funding and service by energy service companies, while offering the value of the net energy savings to the private funders. One example of this can be seen in Wapakoneta, Ohio. An energy-savings performance contract was utilized to fund “repairs for the [SCADA system].”¹² As a result of the agreement, Wapakoneta was able to save over $300,000 in energy costs over the following 10 years.¹²

Conclusion

In order to help cities become more sustainable, a combination of optimized piping, water towers, and SCADA technology should be utilized. Though somewhat costly, these solutions will maximize the water efficiency of a city and help to minimize its maintenance costs. All cities should invest towards developing SCADA technology because it is so crucial for minimizing the water and revenue lost from leakage. They should also take steps to increase dependence on water towers to improve the flexibility of their water distribution systems. Initially, water towers and SCADA may be too expensive for some cities, particularly for smaller, less rich cities. For this reason, smaller cities may want to focus on perfecting the piping design within the city’s households first. As larger cities earn money back from their savings on water waste, they can help to push the development of the smaller cities. Meanwhile, smaller cities can use piping reparations as a temporary alternative to SCADA, reducing the chance of leakage. They can then use the savings they earn through this process to help jump–start SCADA or the building of water towers.