Abstract

The "drive points" made completely of metal also called "Filter Points" are made in a variety of types and their choice depends upon the soil structure in the water-bearing stratum. Ordinarily an inner mesh of size 60 is used in these drive points. The generally advocated type of filter point is made of G. I. material consisting of a sufficient length of G. I. pipes of about 6 feet length and diameter 3" or 4" with holes not more than 1/2" diameter drilled on it at distances varying from 1" to 12" centres. These drilled holes are arranged in a staggered manner and their number and size are limited so that the drive point will not lose its strength. This 6 foot G, I. pipe is closely jacketed with a 60 mesh metal cloth of either copper, brass or galvanised iron. This square mesh cloth is again covered over by a brass or. G. I. perforated sheeting. Both these metal covers are welded or soldered at the top and at the bottom to G. I. pipe to avoid being torn while driving in the filter point. A solid G. I. tip of slightly larger diameter than the drive point itself, to pierce the soil and which when driven down will open up a passage way for the point, is fitted at the bottom of the filter point. On the top of the filter point, a coupling of the correct diameter is screwed and welded. The approximate cost of a 4" size metal filter point ranges from Rs. 129/- to Rs. 130/-.

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