Water Well Journal
Issue link: http://read.dmtmag.com/i/617280
We have already determined through hydraulic modeling the network has 6 PSI of friction loss at a flow of 500 GPM. In addition to this loss, the riser pipe in the well will also lose head due to the resistance between the flowing water and the pipe. Although we have not yet concluded which type of pump we will use, we can provide a rough estimate for our evalua- tion. Typically, I have used 10 feet per 100 feet of pump depth for my estimate. Since our well lift has already been deter- mined at 100 feet, I will use 150 feet of riser pipe length esti- mate for our riser friction loss. The total frictional head loss is thus determined. Network loss: 6 PSI × 2.31 = 13.86 (use 14 feet) + estimated riser pipe loss = 10 feet per 100 feet of pipe × 1.50 (for 150 feet of pipe) = 15 feet of head loss = total of 29 feet. Total dynamic head = Pumping head or well lift = 100 feet System pressure = 140 feet Frictional head = 29 feet TDH = 269 feet 42 January 2016 WWJ waterwelljournal.com WATER WORKS from page 41 Category 1. Water Demands Water usage class: Quasi-municipal (subdivision) Type of usage: Single family residences Number of connections: 100 residences Estimated points of demands: 500, comprised of five people per residence Estimated daily demands (average): 75 gallons per capita day (GPCD) (gallons per person/day) Ancillary demands: (1) Fire protection at 60,000 gallons per event (1000 GPM × 60 minutes duration) (2) Grounds irrigation at 5 acres × .25 inch consumptive use/ day × 27,150 gal/acre-inch (3) Estimated leakage and loss volume = 3% per day Estimated maximum daily demands: × 2.5 (75 GPCD × 2.5 = 188 GPCD) Estimated peak demands: × 2.25 over maximum day demands = 188 GPCD × 2.25 = 423 GPCD Method of handling peak demands: From source and/or supplementary connection to adjacent city Category 2. Source (Well) Parameter: Depth: 250 feet Diameter: 12 inches Casing depth: 200 feet Well casing type: Steel Well screen size: 12-inch T.S. Well screen interval: 200-245 feet Well screen slots: 100 slot Static water level: 50 feet Well seal depth and type: 100 feet/Cement Well yield and pumping level: 1000 GPM at 165 feet PWL (max.) 750 GPM at 130 feet PWL 500 GPM at 90 feet PWL 300 GPM at 72 feet PWL Sand production: None measured at full capacity Well alignment: 16-inch uniform offset over 250 feet in one direction (no doglegs) Table 1. Water System Design Criteria Category 3. Hydraulics Parameter: Discharge pressure: Typ. = 60 psig—Range: 35-70 psig Network loss: 10 psig at 1000 GPM Network loss: 6 psig at 500 GPM Network loss: 3 psig at 200 GPM Required fire flow: 1000 GPM at 25 psig Distribution pipe: 8-inch PVC, I.P.S. Class 160 psi Category 5. Miscellaneous Well access: Clear, off private road Weather protection: Low temperature 10°F Weather protection: High temperature 90°F Onsite sanitary and storm discharge Supplementary water: Provided from adjacent city Storage: Provided from onsite pressure tank for pump control Category 4. Power Supply Voltage: 480 VAC Available full load current: 160 amps Electrical service size: 200 amps Phase: 3 phase Short circuit current: 15,000 amps at transformer Short circuit current: 13,500 amps at pump Transformers: 3 × 50 KVA = 150 KVA Transformer impedance (Z): = 1.2% Allowable max HP without reduced voltage start: 50 HP Type of electrical service: Overhead to safety socket 200 amp meter base (no C.T. metering needed)