UNIVERSITY OF CALIFORNIA • COLLEGE OF AGRICULTURE 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BERKELEY 4, CALIFORNIA 
 
 A NEW IRRIGATION FLOAT METER 
 FOR CONCRETE PIPE LINES 
 
 C. N. JOHNSTON' 
 
 The irrigator who has a water-distributing 
 system made of concrete pipe has little oppor- 
 tunity to measure the water being delivered to 
 his land. As a rule, the flow from the pump en- 
 ters the pipe line directly; it discharges from 
 vertical risers adjoining the field to be irri- 
 gated, without providing a point where flow 
 measurements could be easily made. 
 
 Irrigation Float Meter 
 
 A float meter has been designed suitable for 
 use on the alfalfa valves or orchard valves lo- 
 cated on the riser outlets of such irrigation 
 systems. The construction of these meters pre- 
 sents no difficulty if the details given in the 
 succeeding text are followed. In figure 1, the 
 
 Support stake 
 
 stream from the riser. The lift of any float 
 is determined by the quantity of water passing 
 through the riser, and the weight of the float 
 determines how high it will rise for any given 
 flow. The presence or lack of ponded -water over 
 the discharge face of the alfalfa valve also in- 
 fluences the distance the float is lifted. Tests 
 have been made on 8-, 10-, and 12-inch floats 
 mounted on corresponding sizes of alfalfa valves, 
 both with and without ponding or submersion. 
 Each size float had some minimum weight; to get 
 the effect of varying weight on the lift for the 
 two conditions of submersion or nonsubmersion, 
 additional known weights were added to the 
 floats during the tests. A range of weights for 
 the float is provided so that anyone can pro- 
 
 Concrete riser pipe 
 
 *■ Levelinq slake wth iop le/el wtlh upper 
 
 edae of a/ i alia. \/alve. 
 
 Eig. 1. --Float laeter installed on alfalfa valve, and the accompany- 
 ing lift-indicator scale. 
 
 float meter has been installed on an alfalfa 
 valve which is located on a concrete pipe riser 
 connected to the supply main. The float rises 
 on the brass guide rod (1/4 inch or slightly 
 larger in diameter) , lifted by the outflowing 
 
 Assistant Professor of Irrigation and Associ- 
 ate Irrigation Engineer in the Experiment Station. 
 
 [1] 
 
 duce his own float from whatever materials are 
 available (for example plywood, sheet iron, 
 1-inch planking) and, after obtaining the weight 
 of the assembled float and guide tube, can put 
 it to use. 
 
 In figure 1, equipment is detailed at the 
 left, and a procedure is suggested for obtain- 
 ing the lift of the float whether or not the 
 
 UNIVERSITY OF CALIFORNIA 
 
 LIBRARY 
 
 COLLEGE OF AGRICULTURE 
 DAVIS 
 
alfalfa valve is submerged. The scale is set 
 with its zero resting on the stake, whose top is 
 level with the upper edge of the alfalfa valve 
 when there is no ponding of water to submerge 
 the valve. Then the pointer, if moved down so 
 that its bottom edge is opposite zero, will be 
 just flush with the bottom of the float. When 
 water issues from the valve, the float will rise. 
 Then, if the pointer is moved up and reset so 
 that it is opposite the bottom edge of the float 
 again, it will have been moved the distance of 
 the lift of the float, and the lift can be read 
 on the scale. If, as in figure 1, there is pond- 
 ing above the upper valve face, the procedure 
 would be to move the scale upward until its bot- 
 tom face just touches the surface of the ponded 
 water while flow is in progress; then the pointer 
 should be set opposite the bottom edge of the 
 float and the lift above the ponded water read. 
 A small dam placed around the leveling stake and 
 extending above the water level of the pond, but 
 with a small connection to the pond, will quiet 
 the water under the scale and make the exact 
 positioning of the scale simpler. A metallic 
 cylinder with a few small holes in it, or a strip 
 of sheet iron bent to form a protecting wall also 
 will be effective. These lift readings, plus the 
 known weight of the float assembly, are the only 
 information needed to use the flow curves on the 
 charts. 
 
 The test data for the three disk sizes in- 
 vestigated are summarized in figures 2 and 3, for 
 the 8-inch float; in 4 and 5, for the 10-inch; 
 and in 6 and 7, for the 12-inch. Two figures for 
 each float size are required because submergence 
 or nonsubmergence affects the lift of the float 
 above the valve face. The left-hand side of 
 these figures gives the lift in feet or inches, 
 and the bottom or horizontal line is plotted to 
 weight of the float assembly in pounds. The 
 sloping lines are the plotted locations of the 
 given rates of flow in cubic feet per second 
 (c.f.s.) or fractions thereof. The weight for 
 any given float is a constant and can be readily 
 obtained. 
 
 Assume that two alfalfa valves -- 8- and 12- 
 inch — had been used in the field with the fol- 
 lowing results: 
 
 8-inch 12-inch 
 valve valve 
 
 Weight in pounds . . 1.5 . . 4.5 
 Submergence, if any, 
 
 in inches None. . 3 
 
 Lift in feet .... 0.25. . 0.125 
 
 Lift in inches. ... 3 . . 1.5 
 
 submergence 
 eliminated 
 
 Certain of the test data, figures 2 to 7, 
 will be used in order to determine the flow 
 through the two valve sizes given. From the test 
 data assumed above, the 8-inch float was operat- 
 ing without submergence; therefore figure 2 is 
 used. Since the lift was 3 inches or 0.25 foot, 
 one may start at the left side of the figure at 
 0.25 foot, then move to the right horizontally 
 until a position directly above weight 1.5 
 
 pounds on the bottom line is reached. (See 
 dotted lines in figure 2.) This intersection 
 is found to be slightly above the line corre- 
 sponding to 1.0 cubic foot per second. The 
 flow therefore was approximately 1 cubic foot 
 per second. 
 
 The 12-inch float was operating under sub- 
 merged conditions; that is, the alfalfa-valve 
 face was below the surface of ponded water. 
 Figure 7 covers this situation. Following the 
 same procedure as outlined for the 8-inch 
 valve (see dotted lines, fig. 7), the intersec- 
 tion corresponding to a lift of 0.125 inch and 
 a weight of 4.5 pounds indicates a flow slightly 
 greater than 2.6 cubic feet per second. 
 
 These examples illustrate how to use the 
 graphs for the three sizes of float meters un- 
 der the two conditions of submergence and non- 
 submergence. 
 
 Construction of the Meter 
 
 Two or three cautions and suggestions can be 
 given for the construction of this meter. The 
 guide rod can be made from any smooth shafting, 
 but brass is preferable because it does not 
 swell, rust, or corrode and become rough. Since 
 the guide tube fits the guide rod freely, there 
 is no friction in its passage along the guide 
 rod, and no wobbling of the float either. The 
 guide tube also should be made of brass. It can 
 be soldered to a plate that can be screwed, 
 bolted, or soldered to the float. It is made 4 
 to 6 inches long. The guide rod, about 18 inches 
 long, is centered in the spider in the thread 
 that holds the bolt for tightening the valve 
 cover. Part of an old cover-tightening bolt 
 with the center drilled to take the guide rod 
 makes an ideal support. The float assembly 
 should be as light as possible. Figure 1 shows 
 set screws in use for locking the scale to the 
 stake support and also for locking the pointer 
 to the scale. These are suggestions; some other 
 method may be used. If made of wood, the float 
 should be varnished or painted so that it will 
 not gain weight by soaking up water and will 
 stay flat. A warped float would not be accurate 
 because the edge would not be level; possibly, 
 too, warping would change the lift characteris- 
 tics of the disk. The disk itself seats on the 
 upper face of the alfalfa valve. For an 8-inch 
 alfalfa valve, therefore, the float disk would 
 be about 8 1/4 inches in diameter; for a 10-inch 
 valve, about 10 1/4 inches; and for a 12-inch 
 valve, about 12 1/4 inches. A carpenter's level 
 can be used to set the leveling stake at the 
 correct depth. 
 
 The previous description of submersion as 
 any measured flooding of the face of the dis- 
 charge-valve seat has been somewhat loose. Ac- 
 tually, the curves (figs. 3, 5, and 7) are ac- 
 curate if the submersion for a valve of each 
 given size exceeds the figures in the tabula- 
 tion on page 6. 
 
 [2] 
 
Q" Float 
 No ■submergence 
 
 Fig. 2. --Discharge curves for 8-inch float meter when there is no submergence, 
 
 0.3 
 
 0.2 
 
 0.1 
 
 0.0 
 
 Q" F/ost 
 Submerged 
 
 I Z Pounds 3 4- 
 
 Fig. 3 • --Discharge curves for 8-inch float meter when there is submergence, 
 
10" Float 
 No submergence 
 
 4 S <o 7 
 
 Pounds 
 
 Fig. 4. --Discharge curves for 10-inch float meter when there #s no submergence, 
 
 lo" hloat 
 Submerged 
 
 S G 
 
 Fig. --Discharge curves for 10-inch float meter when there is submergence. 
 
IE" Float 
 No •bubmeroe.nce 
 
 Fig. 6. --Discharge curves for 12-inch float meter when there is no submergence, 
 
 03 - 
 
 12" Float 
 Submerged 
 
 Fig. 7. 
 
 1 2 3 P 4 j 5 G 7 
 
 rounds 
 
 -Discharge curves for 12-inch float meter when there is submergence, 
 
Minimum submergence 
 for accuracy 
 
 8-inch valve . . 1-9/64 inches or 0.0955 foot 
 10-inch valve . . 2-7/32 inches or 0.17875 foot 
 12-inch valve . . 2-25/32 inches or 0.2325 foot 
 
 Below these minimum figures, the curves on the 
 respective charts are not exact. If the operator 
 cannot increase the submersion above these mini- 
 mums by creating an obstruction to the exit from 
 about the valve, he can obtain accurate readings 
 in the following manner, using the curves on 
 figures 8, 9, and 10. If an 8-inch valve were 
 in use, the following data would be obtained: 
 weight of float, 2 pounds; submersion, 0.05 foot 
 or 0.6 inch; lift with submersion eliminated, 
 0.2 foot or 2.4 inches. 
 
 When the submersion is less than the minimum 
 of the 1-9/64 inches for the 8-inch valve, as in 
 the data just given, the quantity being dis- 
 charged for the lift specified is somewhere be- 
 tween that given for no submergence in figure 2, 
 and that given for above -minimum submergence in 
 figure 3 (the two 8-inch-float curve sheets). 
 Figure 8 supplies the data to show just how much 
 this amount of submersion (0.2 foot) is shifted 
 from the nonsubmerged conditions toward the 
 submerged. 
 
 In figure 8, the lower or horizontal leg of 
 the graph shows the submersion; starting at the 
 measured value, 0.6 inch, one goes vertically 
 
 (see dotted line) to the diagonal curved line. 
 From this intersection one moves horizontally to 
 the left-hand side of the graph, making an inter- 
 section at the percentage 63.5 (as nearly as can 
 be read). Turning now to figures 2 and 3, and 
 traveling up from the bottom line at weight 2 
 pounds (the weight of the float used) to a hori- 
 zontal line from lift 0.2 foot, and the following 
 data result: nonsubmerged flow, 0.94 c.f.s.; 
 submerged flow, 1.08 c.f.s.; ratio of submerged 
 
 1.0 
 
 and nonsubmerged flow, 
 
 0.94 
 
 1.15; possible 
 
 error, 15 per cent. 
 
 The nonsubmerged float gives less flow than 
 the submerged. The difference between the flows 
 found (1.08 - 0.94) is 0.14 c.f.s. The 63.5 per 
 cent found by using figure 8 (above) is used to 
 correct this difference and to permit an accurate 
 reading of discharge. The correction is 0.14 x 
 0.635 = 0.0889, or 0.09 c.f.s. Because this 
 correction is from nonsubmerged toward submerged 
 conditions, the 0.09 c.f.s. is added to the 0.94 
 found on the nonsubmerged curve sheet, and 1.03 
 c.f.s. is the corrected reading. This procedure 
 would be followed whenever the submergence for 
 any test is found to be below the minimum for a 
 float of the size in use, unless the submersion 
 can be increased by backing up the flow a little 
 as it leaves the pond that causes the submersion. 
 
 Figures 8, 9, and 10 need not always be used, 
 for the error is relatively small. 
 
 EIGHT- I'!Cr FLOfT METER TEST 
 
 100 
 
 
 
 
 
 80 
 
 
 <-- - - 
 
 
 
 60 
 
 
 
 A 
 
 
 40 
 
 
 
 
 \ 
 
 20 
 n 
 
 — / 
 
 1 
 
 i 
 
 1 1 
 
 O.C in. 
 
 O.f. in. 0.9 in. 
 
 1.2 in. 
 
 0.026 i't. 
 
 0.02-0 ft. 0.075 ft. 
 DEPTH SUBMERGED 
 
 0.10C ft 
 
 Fig. 8. --Curve shows tendency of partial submergence 
 to shift flow readings from nonsubmerged conditions 
 toward submerged. When shift becomes complete or curve 
 has risen toward right to a horizontal from 100 per 
 cent on left-hand side of figure, the submergerce has 
 reached the minimum value. 
 
 [6] 
 
TWELVE -INCH FLOAT METER TEST 
 
 - 
 
 100 ^^ 
 
 - 
 
 80 ^ 
 
 - 
 
 60 ^^"^ 
 
 - 
 
 40 
 
 - 
 
 20 / 
 
 1 1 1 1 1 1 1 1 1 1 
 
 0.3 in. 
 
 0.6 in. 
 
 0.9 In. 
 
 1.2 In. 
 0.100 ft. 
 
 1.5 in. 
 
 1.8 in. 
 
 2.1 in. 
 
 2.4 in. 
 
 0.200 ft. 
 
 2.7 in. 
 
 3.0 in. 
 
 DEPTH SUBMERGED 
 
 Fig. 9. --Curve shows tendency of partial submergence to shift flow readings 
 from n on submerged conditions toward submerged. When shift becomes complete or 
 curve has risen toward right to a horizontal from 100 per cent on left-hand side 
 of figure, the submergence has reached the minimum value. 
 
 
 
 THI-IICH FLOAT METER TEST 
 
 100 
 
 - 
 
 
 80 
 
 - 
 
 
 60 
 
 
 >^ 
 
 40 
 
 - 
 
 
 20 
 
 
 / 1 
 
 1 1 1 1 1 1 
 
 0.3 in. 
 
 0.6 in. 
 
 0.9 in. 
 
 1.2 In. 
 
 1.6 in. 
 
 1.8 in. 
 
 2.1 in. 
 
 0.026 ft. 
 
 0.060 ft. 
 
 0.076 ft. 
 
 0.100 ft. 
 
 0.126 ft. 
 
 0.160 ft. 
 
 0.176 ft 
 
 DEPTH SDHMEROED 
 
 Fig. 10. --Curve shows tendency of partial submergence to shift flow readings from nonsubmerged con- 
 ditions toward submerged. When shift becomes complete or curve has risen toward right to a horizontal 
 from 100 per cent on left-hand side of figure, the submergence has reached the minimum value. 
 
 4m-Nov. , * 45 (61771 
 
Digitized by the Internet Archive 
 
 in 2012 with funding from 
 
 University of California, Davis Libraries 
 
 http://archive.org/details/newirrigationflo59john