Water Well Journal
Issue link: http://read.dmtmag.com/i/617280
a reserve rate. Following this three-part series on pumping system design, this factor will be discussed in a future article. This is a simplistic discussion regarding a generally com- plex matter. Each water system has its own unique challenges and design factors that must be considered, evaluated, and included in the design in one form or another. Step 2: Determine the Required Pumping Head Now that we know the required pumping capacity needed from the well and well pump, we must evaluate and determine the required head from the pump. Although many water sys- tem designers prefer to use the somewhat interchangeable terms of head or pressure, as an engineer I always prefer to use head for all of the design factors. In our example, we will be examining both a vertical tur- bine pump and a submersible pump, so we must use factors that will apply to both types of pumps when calculating the head. Well lift Normally, I like to begin with the source to determine the needed vertical lift the pump must withstand. From our sec- ond design factor, the source, we can see the well produces 500 GPM from a lift of 90 feet. Although this value may rep- resent the actual lift for this flow rate, in most cases I prefer to add some reserve lift to account for dry years, added inter- ference from neighboring wells, or future well incrustation. In this case I will assume the lift to be 100 feet of head, aka pumping head. + System pressure The second head design factor is usually the only place I may stray a bit and use pressure as a starting point since the water system is generally equated in PSI. In our example, the typical design operating pressure we were asked to design for is 60 PSI with a range of 35-70 PSI. A conversion to head provides: 60 PSI × 2.31 feet/PSI = 138.6 feet of head (use 140 feet). + Frictional head The last design factor we need to consider to determine head are the various kinds of frictional losses within the pumping and delivery system. In our example there are two types of friction loss: the losses associated with the pump simply delivering the water to the surface, and the losses within the water system itself. Twitter @WaterWellJournl WWJ January 2016 41 WATER WORKS continues on page 42 National Groundwater Awareness Week Promote the resource that provides your livelihood! Educate your customers about the importance of annual water testing and well maintenance during National Groundwater Awareness Week, March 6-12, 2016. You will be helping them, yourself, your business, your industry, and the resource. NGWA is here to help you spread the word! From sample letters-to-the-editor and radio spots to print ads, posters, and iers, NGWA has materials for you to use. Find out how you can help spread the word! NGWA.org/AwarenessWeek 800 551.7379 • 614 898.7791 The Groundwater NGWA Association SM DACUM Codes To help meet your professional needs, this article covers skills and competencies found in DACUM charts for drillers and pump installers. PI refers to the pumps chart. The letter and number immediately following is the skill on the chart covered by the article. This article covers: PIA-2, 3, 4; PIB-1, 3, 4, 5, 6, 8, 9; PIC-1, 5, 6, 7, 8, 9 More information on DACUM and the charts are available at www.NGWA.org.