Water Well Journal

January 2016

Water Well Journal

Issue link: http://read.dmtmag.com/i/617280

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Page 39 of 67

O ur last two installments of The Water Works provided overviews of the two most common types of large pumps used in water well applications to satisfy most of today's industrial, municipal, and agricultural irrigation water demands. Namely, vertical turbine pumps (July 2015 WWJ) and submersible pumps (October 2015 WWJ). The next three installments will expand upon the two pre- vious articles and apply both types of pumps to the same real- world example. Please remember my intent is to present typical design ele- ments based on my prior experience and is not to be inferred as the only method to be used to successfully create a water system or pumping plant. While there are many fundamental rules to the design of a hydraulic or pumping installation that seem to be fairly universal, there are also various rules of thumb, local or regional codes, and local traditions that will or can modify other less critical elements. Only by having adequate experience and training can anyone be assured they will be able to employ any of these variables to their design. When in doubt, it is recommended individuals consult with someone with more knowledge and experience in the design of water systems. The System Parameters As a water system engineer who has designed more than a thousand water systems, I learned the hard way a designer must have full knowledge of all the parameters associated with the intended installation to ensure the water system functions as intended. Whether the water system is a single small pump installa- tion planned for a single family of four, or a large water system with 25 pumping stations built to provide water to thousands of people, all the data needed for a successful water system must be provided. Beyond the basics of capacity and the head (pressure) needed, the designer must verify other more seemingly mundane factors such as the well parameters of alignment, diameter, depth, and static and pumping water levels. System parameters needed are the power supply including voltage, phase, available current, and available short circuit current; hydraulics and piping including the size, length, and "C" factor of the discharge piping; head loss through the water system network; and elevation rise or fall within the water system. These factors represent a few but not all of the many vari- ables associated with a satisfactory design. In our design example, we are charged with the design of a new water system planned for a new subdivision development of 100 homes on the edge of a large municipality (Figure 1). In this case, assume the entire development will be served from a single well located roughly in the center of the sub- division. Serving this many homes from one single well and pump in reality will generally represent an excessive risk to reliabil- ity, redundancy, fire protection, and an adequate capacity range—which would usually necessitate strong consideration of an elevated reservoir, a ground-level reservoir and booster pump station, or additional wells. However, we will assume for simplicity's sake this particu- lar water system has been equipped with a supplementary water connection to a nearby city to provide additional water by use of an automatic cut-in valve during the event of a power loss or low pressure. Therefore, this factor has been considered and one well and well pump for most water demands is deemed to be adequate. We will discuss supplementary water storage or sources for fire and peak demands in a future article of The Water Works. This type of water system is not that rare in life and is fre- quently used when one water system abuts another. In practice, there are numerous considerations that must be addressed in the design of a water system. In my experience I generally examine five major categories, each having their own subset of factors. These five categories include: 1. The water demands: The volume, rate, destination, and use of the water pumped from the source. This can be a multitude of uses including domestic or municipal water demands, commercial/industrial uses, and irrigation uses. 2. The source: Typically a water well (Figure 2), but in some cases may be a surface water source or even a con- nection to another water system. ED BUTTS, PE, CPI THE WATER WORKS ENGINEERING OF WATER SYSTEMS Part 12(c)—Pumping System Design The first step in designing a functional water system is to determine the required capacity from the source , bearing in mind there is an upper limit to the safe source capacity. 38 January 2016 WWJ waterwelljournal.com

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