UNIVERSITY OF CALIFORNIA • COLLEGE OF AGRICULTURE 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 BERKELEY 4, CALIFORNIA 
 
 THE PORTABLE IRRIGATION SIPHON AND 
 A NEW PRIMING VALVE FOR SIPHONS 
 
 C. N. JOHNSTON 1 
 
 The war-induced shortages of labor and materi- 
 als have stimulated the search for simpler 
 methods of irrigating to eliminate labor, and 
 for substitute materials and equipment to re- 
 place items no longer available. Thousands of 
 2-inch siphons (fig. l) made of metal, plywood, 
 or plastic have been used in recent years, 
 
 Siphon 
 
 Figure 2 gives test data resulting from in- 
 vestigation of several 2-inch siphons having 
 smoothly finished inside joints at the bends. 
 Any 2-inch siphon of like construction should 
 give similar performance. Siphons with rough 
 inside joints will perform less well than smooth 
 ones and will give less flow for any given head 
 
 Wale 
 
 Fig. 
 
 %W' 
 
 1. --Two-inch siphon made of metal, plywood, or plastic, 
 
 mainly to irrigate row crops such as tomatoes, 
 beets, and beans. The chief advantage of siphons 
 is to permit the water to pass from the ditch 
 over the ditch bank into the field without cut- 
 ting into the bank. One man, handling a maximum 
 of 150 siphons, can easily irrigate an area that 
 would otherwise require two or more men for 
 shoveling banks and attending to ditches. The 
 handling of large-size siphons is laborious part- 
 ly because of difficulties in their priming. To 
 overcome this, a priming valve has been designed 
 to be used with 2-inch or larger siphons. 
 
 Portable Two-Inch Siphon 
 
 The first problem of the new user of these 
 siphons is to decide how many he needs. The 
 discharge of each one becomes greater along with 
 the net head in inches; that is, the flow in- 
 creases when the distance from the water surface 
 in the field up to the water level in the ditch 
 has increased. This difference in the two water- 
 surface elevations is the head. For any given 
 installation, there is a limit to the amount of 
 head; the greater the head, the more likely the 
 ditch is to leak through the banks and wash out. 
 Claylike banks are safer for high heads than 
 sandy banks. 
 
 Assistant Professor of Irrigation and Associ- 
 ate Irrigation Engineer in the Experiment Station. 
 
 (perhaps as much as 10 per cent less flow). 
 Table 1 furnishes the same data as figure 2, but 
 only for selected heads and corresponding flows. 
 The graph is actually the complete picture of 
 the performance of the 2-inch siphon. 
 
 The irrigator not only must decide how many 
 siphons are necessary, but he also must know 
 how much head is safe and how much water the 
 group of siphons should deliver from the ditch 
 to keep up with the supply. For example, if 
 1.5 cubic feet per second (c.f.s.), or roughly 
 675 gallons per minute (g.p.m.), are supplied 
 by a pump, and a head of 3 1/2 inches is safe 
 from ditch-water level to field-water level, he 
 must know how many siphons are needed to use 
 this supply. 
 
 Figure 2 shows inches of head on the vertical 
 or side line, and gallons per minute on the 
 horizontal or bottom line. Since the safe head 
 is 3 1/2 inches, one may. start at this point on 
 the chart and move horizontally to the slope 
 line. At this point direction is changed; going 
 straight down a vertical line, the bottom line 
 is joined at 27.8 g.p.m. For computation, using a 
 lower value, such as 27.5, would provide a margin 
 of safety. Then, the problem of how many siphons 
 handling 27.5 g.p.m. would be required to provide 
 1.5 c.f.s., or 675 g.p.m. is solved as follows: 
 
 = 24.5 or 25 siphons. 
 
 LI] 
 
 27.5 
 
 the result will be the same 
 
 UNIVERSITY OF CALIFORNIA 
 
 LIBRARY 
 
 COLLEGE OF AGRICULTURE 
 
 DAVIS 
 
 If table 1 is used. 
 
10 
 
 e 
 
 
 
 7* 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3.5V/7c/> head 
 
 "7 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 1 
 
 
 
 
 
 • 
 
 
 
 
 
 r i 
 
 
 
 
 
 
 
 
 
 
 ii 
 
 
 
 
 
 
 
 
 
 
 0*| 
 
 s> 1 
 
 l-» * 
 oa i 
 
 
 
 
 
 
 
 
 10 
 
 IS 20 30 4 50 «0 70 80 90 100 
 
 6affons per minute. 
 
 Fig. 2. --Test data from several similar 2-inch siphons showing average performance. 
 
TABLE 1 
 Heads and Capacities for Two-Inch Siphons 
 
 Head(h) 
 
 Discharge 
 
 Head(h) 
 
 Discharge 
 
 in 
 
 in 
 
 in 
 
 in 
 
 inches 
 
 g.p.m. 
 
 inches 
 
 g.p.m. 
 
 0.8 
 
 13.0 
 
 5.5 
 
 35.0 
 
 I . J 
 
 14.5 
 
 6.0 
 
 36.8 
 
 1.5 
 
 17.9 
 
 6.5 
 
 38.1 
 
 2.0 
 
 20.8 
 
 7.0 
 
 39.8 
 
 2.5 
 
 23.4 
 
 7.5 
 
 41.1 
 
 3.0 
 
 25.6 
 
 8.0 
 
 42.7 
 
 3.5 
 
 27.8 
 
 8.5 
 
 44.0 
 
 4.0 
 
 29.7 
 
 9.0 
 
 45.2 
 
 4.5 
 
 31.7 
 
 9.5 
 
 46.5 
 
 5.0 
 
 33.3 
 
 10.0 
 
 47.9 
 
 Although the minimum number of siphons is 25, 
 a few more will be needed. The operator will 
 not wish to shut down his pump; so, if he has 6 
 to 12 additional siphons, he can use them when 
 he is ready to move to another field. He will 
 start the extra ones in the new location, pick 
 up some of those finished at the first field, 
 put them in operation at the new field, return 
 for the rest at the old field, and continue this 
 process. He will start each siphon by dipping 
 one end into the ditch while holding his hand 
 over the other end — the highest point on the 
 siphon, although it is now being held as low as 
 possible. He will make two or three longitudinal 
 thrusts with the siphon, forcing the submerged 
 end quickly through the water with each thrust. 
 Since his hand over the unsubmerged end acts as 
 a valve, the displaced air caused by the thrust 
 escapes under pressure but is not allowed to re- 
 turn. When the water reaches his hand at the 
 upper end of the siphon, the siphon is lowered 
 to the field, and then his hand is removed. Flow 
 begins at once. 
 
 Siphons 3 and 4 inches in diameter are light 
 enough in weight to be managed by hand, but 
 difficult for one man to prime unassisted. They 
 give discharge rates greater than the 2-inch 
 size. The capacities of 2-, 3-, and 4-inch 
 siphons may be roughly compared as follows: 
 
 Relative 
 capacity 
 
 2-inch siphon 1 
 
 3-inch siphon 2 1/4 
 
 4-inch siphon 4 
 
 One can infer that the 3-inch siphon will de- 
 liver about 2 1/4 times as much as the 2-inch 
 for the same head, whereas the 4-inch will de- 
 liver about four times as much as the 2-inch at 
 a constant head. 
 
 Priming Valve for Siphons 
 
 One can prime 2-inch siphons by using the 
 hand as a valve over the upper end of the siphon 
 tube. Since, however, the hand cannot readily 
 
 close larger units at the end, other expedients 
 must be introduced. A common practice has been 
 to slip a tight-fitting canvas sleeve, a foot 
 or so long, over the field end of such siphons 
 for 2 or 3 inches. Then, after the whole siphon 
 is submerged in the ditch, the loose or open end 
 of the canvas sleeve is folded or rolled up, or 
 is bound with twine or wire to form a seal. Then 
 the field end of the siphon is lifted from the 
 ditch into the field, and, when the seal is re- 
 leased, the flow starts. A man can accomplish 
 this process with siphons up to about 4 inches 
 in diameter. With a larger diameter, however, 
 more energy is demanded; a car, truck, or tractor 
 often can supply the needed power to move the 
 sealed end over to the field side of the ditch 
 bank. 
 
 To expedite the priming of 3- and 4-inch si- 
 phons, and to facilitate the use of larger sizes, 
 the priming valve mentioned in the introduction 
 has been developed to replace the canvas sleeves 
 and hasten the priming process. This valve 
 (fig. 3) accomplishes the same purpose as does 
 the hand with the 2-inch siphons. It consists 
 of a tapered plug (b) which fits the inside of 
 the siphon (a) and forms a seal; a spring-loaded 
 flat disk valve (d) seats on the outer face of 
 the plug. The plug itself is wrapped with sheet 
 rubber (c) or similar seating material. The 
 shroud (h) protects the valve and valve stem, 
 and diverts the water away from the operator 
 when the siphon becomes full during the surging 
 action involved in priming. Without the shroud, 
 the water ejected from under the valve disk 
 would spray the operator. The valve shown in 
 figure 3 is of masonite , with a rubber facing 
 made from an old inner tube. The* valve seat on 
 the plug was machined smooth. 
 
 The materials and design details used in the 
 priming-valve assembly shown in figure 3 are 
 suggestions only. A light-weight metal disk 
 could be substituted for the masonite disk of 
 the valve, and rubber facing might not be needed 
 to improve the seal. The disk (d) could seat 
 on b if e. were located outside of b. The shroud 
 then would be soldered to e. Or e might even 
 be eliminated if the shroud (h) could be shaped 
 beyond where h joins b so there would be about 
 l/4-inch clearance between the valve disk and h. 
 Twine or wire may be used to fasten sheet rub- 
 ber or similar sheet material to the tapered 
 face of the plug. The rubber facing for the 
 valve disk can be cemented on with cellulose 
 cement . 
 
 Dimensions are not critical for any part of 
 the priming valve so long as there is a suffici- 
 ent opening for the release of air. The spring 
 load (f) is light (only a few ounces). The 
 valve disk may work on a hinge instead of being 
 center-guided and loaded. After the assembly 
 is placed at the end of a siphon, priming is 
 accomplished at the surging action previously 
 described for the 2-inch units. If the valve 
 seats tightly on the plug seat, two or three 
 good surges are sufficient to prime a siphon of 
 
 [3] 
 
manageable length. The use of such valves 
 might make the priming of 3- or 4-inch siphons 
 as rapid in the field as the hand-priming rate 
 for the 2-inch type. Only one priming valve 
 
 needs to be made for use with a large number of 
 siphons of a given size because the valve unit 
 is removed after each priming, and is carried 
 along by the operator to the next siphon. 
 
 CL 
 
 Fig. 3 • --Priming valve for siphons. The dimen- 
 sions of the parts are dependent on the size of 
 siphon to be fitted. 
 
 [4] 
 
 4m-Nov. , ' 45 (6178)