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Determining the Capacity of a Pump

Elizabeth Kaiser : Wed, Aug 22, 2012 @ 08:08 AM

Whether you are flood irrigating, flooding a duck pond, or just determining your pump capacity, it is good to know the measure of your pumping performance. Below is a table of estimated performance for Crisafulli pumps.

Number of Acres Covered in Twelve Hours Pumping

GPM	cu ft/sec.	cu ft/sec.	1" deep	2" deep	3" deep	4" deep	6" deep	8" deep	10" deep	12" deep
20	.05	2.68	.53	.27	.18	.13	.09	.66	.05	.04
60	.11	6.68	1.33	.66	.44	.33	.22	.17	.13	.11
100	.22	13.4	2.65	1.33	.88	.66	.44	.33	.27	.22
160	.34	20.1	3.98	1.99	1.33	1.0	.66	.50	.40	.33
220	.50	30.1	5.97	2.99	1.99	1.5	.99	.75	.60	.50
300	.67	40.0	7.96	3.98	2.67	2.0	1.33	1.0	.80	.66
400	.90	53.4	10.6	5.31	3.54	1.78	1.77	1.33	1.1	.08
700	1.6	93.5	18.6	9.28	6.18	3.1	3.1	2.32	1.9	1.5
900	2.0	120.4	23.9	11.95	7.96	6.0	4.0	3.0	2.4	2.0
1200	2.7	160.5	31.8	16.0	10.6	8.0	5.3	4.0	3.2	2.7
3000	6.7	400.5	79.5	39.75	26.5	20.0	13.3	10.0	8.0	6.6
10000	22.3	1337.0	265.0	132.5	88.3	66.3	44.2	33.2	26.5	22.1

BY HORIZONTAL OPEN DISCHARGE METHOD

To estimate the pumping capacity of any given unit, construct an L-shaped measuring instrument similar to the one shown in the sketch. The shorter side should be 4" long. The longer side may be any convenient length marked in inches. With the water flowing from the horizontal open discharge, place the long side of the L along the top of the discharge pipe, allowing the shorter side to hang downward as shown in the drawing. Slide the L along the pipe until the 4" length barely touches the flow of water. Note the distance travelled ("X") by the flow of water before it drops 4". Presume, for example, that the distance travelled is 15" and the inside diameter of the pipe is 3". Consulting the table below, locate 15" in the fisrt column (Horizontal Distance X(inches()). Then move horizontally to the column labeled 3 (pipe diameter used). Thus, for our hypothetical unit the pumping capacity is approximately 183 gallons per minute.

First Column = Horizontal Distance X (inches)
First Row = Nominal Pipe Diameter (inches)
Last Column = Average Velocity

	1	1.25	1.5	2	2.5	3	4	5	6	8	10	12
4	6	10	13	22	31	49	84						2.1
5	7	12	16	28	39	61	104	163					2.6
6	9	15	20	33	47	73	125	195	285				3.0
7	10	17	23	39	55	85	146	228	334	580			3.7
8	11	20	27	44	63	&98	166	260	380	665	1060		4.2
9	13	22	30	50	70	110	187	293	430	750	1190	1660	4.7
10	14	25	33	56	78	122	208	326	476	830	1330	1850	5.3
11	16	27	36	61	86	134	229	360	525	915	1460	2200	5.8
12	17	29	40	66	94	146	250	390	570	1000	1600	2220	6.2
13	19	32	43	72	102	158	270	425	620	1080	1730	2400	6.9
14	20	34	47	77	109	170	292	456	670	1160	1860	2590	7.4
15	21	36	50	83	117	183	312	490	710	1250	2000	2780	7.9
16	23	39	53	88	125	196	334	520	760	1330	2120	2960	8.4
17		42	57	93	133	207	355	550	810	1410	2260	3140	9.1
18			60	99	144	220	375	590	860	1500	2390	3330	9.7
19				110	148	232	395	620	910	1580	2520	3500	10.4
20					156	244	415	350	950	1660	2660	3700	10.6
21						256	435	685	1000	1750	2800		11.4
22							460	720	1050	1830	2920		11.8
23								750	1100	1910	3060		12.4
24									1140	2000	3200		13.0