9 THREE BASIC QUESTIONS FOR SIZING: PUMP SIZINGTHREE BASIC QUESTIONS FOR SIZING:1. HOW MUCH ( Demand)2. HOW HIGH ( Static Head)3. HOW FAR ( Friction Head)
10 Calculating System Demand ( HOW MUCH)POPULATION METHOD:Formula: ((NP x 100 gal/day/person x 4 )/24hrs/day )/60 min/hr. = GPMNP = population served Number 4 is the peak flow factorExamples: 80 people in a sub-division.((80 x 100 x 4)/24)/60 = 23 GPM.
11 Calculating System Demand FIXTURE COUNT METHOD:Each fixture in a building is given a “ unit weight”.The total “unit weight” of all the fixture in thebuilding is referenced on a conversion graph and a gallons per minute flow is determined.
12 Static Head ( How High) Discharge Point Discharge Line Static Head = Elevation ChangeStatic HeadPump
13 Friction Head ( HOW FAR) Discharge Point Discharge Line Friction head is determined by adding the total lengthof the discharge line (including fittings) then referencing a friction loss chart . Using the system demand flow and the size of the discharge pipe, the total head loss can be found.PumpTOTAL DYNAMIC HEAD = Static Head + Friction Head
14 Discharge Pipe Selection MINIMUM FLOW VELOCITY: In order to keep solids flowing in a horizontal pipe, a velocity of 2 ft. / sec. must be maintained.2 ft./sec flowPipeSuspended SolidsFlow rates required to maintain 2 ft./sec:2” pipe = 21 gpm 3” pipe = 46 gpm 4” pipe = 80 gpm
15 Discharge Volume Exchange To Find volume in Discharge line: Length of discharge ( ft.) X gal/ft. = Gal in LineSewer MainDischarge LineLiquid Volume in Pipe: 2” = .17 gal/ft.3” = .36 gal/ft.4” = .65 gal/ft.Pump
16 Pump and System CurvesCombined Pump and SystemCurvesSystem Curve
17 Basin Sizing & Selection 1. Physical Dimensions : Will it Fit ?
18 Discharge Volume Exchange Liquid Volume in Pipe: 2” = .17 gal/ft.3” = .36 gal/ft.4” = .65 gal/ft.To Find volume in Discharge line:Length of discharge ( ft.) X gal/ft. = Gal in LineBasinSewer MainDischarge LinePump onDraw downPump offPumpThere should be enough draw-down to change thevolume in the discharge line every cycle.
19 Discharge Volume Exchange Liquid Volume in Pipe: 2” = .17 gal/ft.3” = .36 gal/ft.4” = .65 gal/ft.To Find volume in Discharge line:Length of discharge ( ft.) X gal/ft. = Gal in LineBasinSewer MainDischarge LinePump onDraw downPump offPumpThere should be enough draw-down to change thevolume in the discharge line every cycle.
20 Basin Sizing Calculations EXAMPLE: Commercial building with 50 gpm flow rate. Pump selected has a flow rate of 60 gpm. The pump height is 18” and the invert is 8”. The discharge line is 3” in diameter and 150 ft long.Step 1. Invert Distance - 8”Step 2. Pump Height ”Step 3. Draw down ( largest of the following )a. Max starts – (( 50 gpm x 60 min )/ 6) x .4 = 200 gal/cycle200 gal / 4.4 gal per inch = 45”b. Volume in discharge gal / ft x 150ft = 54 gal54 gal / 4.4 gal per inch = 12”c. Pump run time : (60 gpm x 1 Min) / 4.4 gal per inch= 14The total of all three critical dimensions is 71” The closest basin depth is 72”. Thus the suggested basin is 36 x 72. If this depth is too great for the application, then a wider basin can be used. This would result in a shallower basin.
21 Calculating Depth 36” diameter basin: Floor level 8” Invert Inlet pipe 45”(Draw down)PumpNote: This would result in a complete change of volume and a run time of 3.5min18”
22 Residential RealityThe preceding examples work well for commercial applications and for those residential applications serving the whole house. The reality is that most residential sewage applications serve just one, seldom used bathroom. In these applications the usage is so small that the pump protecting guidelines do not have the same importance. In these applications, a 2” solids pump and an 18 x 30 poly basin work very well.
23 VENTS AND AIR ADMITTANCE VALVES Related TopicsVENTS AND AIR ADMITTANCE VALVESVent to atmospherePotential confined airLiquid InflowStudor AAVWater levelIncoming liquid displaces air, which is released through the vent. AAV’s prevent this release, causing the system to “air lock”.
24 Questions For Additional Information: Chris Beiswenger (317)