OCR Text |
Show SCREENS AND POINTS Must Be Used in Thick Sand and Gravel Beds. In Digging Wells for Irrigation Screens 8hould Not Be Ordered More Than Ton Feet In Length Easier to Handle, Screens or slotted points must bo usod In sand or gravel beds, especially If thd bods aro thick ones. In vory thick bods two or moro soctlona of Bcreon, ono above tho othor, should bo usod. Such scrons aro often made In soctlons, so that thoy can bo screwed together on tho spot. Complotod screens are now regularly mado by tho woll point manufacturers In consider-able consider-able longths, reaching to 20 feet or a full pipe length. Tho small size points aro mado from standard wrought plpo, In which holes havo been punched, covorcd with brass wlro cloth and perforated per-forated brass Jackot to protect tho cloth. Tho largest woll point machines do not, as a rulo, nandle ovor 10-lncli pipe. If larger than this, holes must bo drilled, which Increases cost rap-Idly. rap-Idly. For convonlonco In handling, shipping and pluclug, screens should not bo ordered over ten feet In length. This length Is preferred by tho trado, says tho Pumps and Supplies. If a single screen will not furnish wator onough, or If tho water bearing strata is not deep onough, two or moro scroon points may bo sunk independent independ-ent of oach othor and far onough apart so that they will not Interforo or rob ono nnother. Theso screens may then bo connected to a common suction plpo or arranged to druln Into a common com-mon central well. Screen points, as a rule, should nevor bo less than two-thirds two-thirds the diameter of tho cylindor, and for work of this character it is always al-ways hotter if thoy aro as largo as tho cylinder; tho moro screno surface tho morow nter will come through. It has boon found that ttio coarsest sand and gravol Is froquontly at the bottom of tho water-bearing strata; henco it is Important that tho screen point should roach into tho bed of this coarso material. It is well undorstood that water flows moro trooly through tho coarso sand and gravol and that tho screen will not clog up. Then, too, deop driving protects tho well against lowering of tho wator level by othor wolla In tho immediate vicinity, or on tho samo vein some distance away. In river bottoms, whero water-bearing sand is sometimes found 100 feet or moro In thickness, it would not be necessary to put a screen point down to tho bottom of tho strata.; but close attention should bo given, howovor, In such cose to the relntlve coarseness of tho sand or gravel in which tho scroon 1 point is lodged. Under no clrcum-stancos clrcum-stancos should it bo sot in anything but the coarsest. Tho top of tho screen point in any caso should bo some dlstanco bolow tho wator lovol. Tho wator lovel will bo, of courso, tho height to which tho wator rises in tho woll, but on being pumped this lovel may drop It generally gen-erally doos so henco It Is necessary to put tho scroen so low that it will bo bolow tho wator lino even whon supplying sup-plying tho greatest amount of water It can furnish. By keeping tho screen sufllclontly low, any danger from tho admission of nlr will bo avoldod. |