The following U.S. military report on the German WWII Tornisterfiltergerät, a portable haversack filter, was originally published in Tactical and Technical Trends, No. 38, November 18, 1943. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

GERMAN PORTABLE HAVERSACK FILTER The Tornisterfiltergerät, a portable haversack filter, is standard equipment in the German army, and is issued on a company basis. The filter is said to be able to treat from 22 to 55 gallons of water per hour, according to the amount of solid matter contained. Although the Tornisterfiltergerät was designed primarily for clarification of water it is claimed by the Germans that this device will effectively treat water that has been contaminated by dead bodies and similar substances; however, it is expressly stated that the filter will not rid water of objectionable odors nor is it effective against water containing chemical warfare agents or substances in solution. Methods of water purification used by the United States and Japanese armies were described in Tactical and Technical Trends, No. 22, p. 33. a. General The gross weight of the filter and accessories is approximately 45 pounds. The whole assembly is packed in a canvas case, provided with two carrying straps so that it may be carried on the back, haversack-fashion. The assembly consists of two parts, viz., spares and accessories box shown at (1) in the accompanying sketch, and the filter; the box contains six pockets, each of eight spare filter pads; also a cleaning brush and instruction manual. The filter consists of a chamber through which water is forced by means of a pump (2), actuated by a handle (3), the grip of which is hinged and can be set at right angles to the shaft, as shown. The pump is supplied with water through a reinforced rubber intake pipe (4), terminating in a metal strainer (5). The standard length of the intake pipe is probably about 6 feet 7 inches. Water is delivered to the filter chamber through the delivery pipe (6). The filter chamber is contained between a front plate (7) and rear plate (8) which are held together by four tie-bolts and wing nuts (9). The two lower bolts are hinged to the rear plate and they can be swung outwards when the filter chamber is to be dismantled. The wing nuts can be tightened by means of a key (10) which is normally located on the bar (11). At (12) on the front plate is an air valve, with a safety valve (13) and (14) the water outlet. Inside the filter chamber are four screens (15), provided at one side with top and bottom annular porcelain projections which fit together when the screens are in position, forming a continuous water channel. Alternating with four screens (15) are three frames (16), also fitted with annular porcelain projections. Between each screen and frame, and between the two outer screens and the front and rear plates, are eight filter pads (17). b. Method of Operation Water is sucked by the pump (2) into the strainer (5) and intake pipe (4) through the delivery tube (6), past the air valve (12) and safety valve (13) into the upper and lower channels formed by the porcelain projections on the frames (16). From each of these two channels three small openings (18), one in the center of each porcelain projection, lead to the inside of the frame; the water is forced through these and then through the filter pads (17) into the screens (15), where it goes into the upper and lower channels formed by the porcelain projections on the screens, and can be collected at the water outlet (14). c. Method of Assembly Remove and roll up the canvas cover. Unscrew the 4 wing nuts, Move the 2 lower tie-bolts outwards. Pull the front plate (7) forward. Remove the screens (15) and frames (16). Insert 8 filter pads in position so that they rest on the cross bars on the lid of the spares and accessories box, so that the rough side of the pad faces toward the frame. Push back the front plate (7). Swing the 2 lower tie-bolts back into position on the front plate. Tighten the wing nuts, first by hand and finally with the key (10). Place the strainer (5) in the water, making sure that it does not sink into mud. Open the air valve (12) by putting the handle in the vertical position. Fix the grip on the pump handle (9) at right angles to the shaft, and begin to pump slowly. As soon as water issues from the air valve, close the valve and continue pumping until water begins to issue from the outlet (14). d. Changing Filter Pads Cease pumping. Open the air valve. Unscrew the four wing nuts. Dismantle the front plate, screens and frames. Remove, and if possible, bury the used filter pads. Carefully rinse down the front and back plates, screens and frames, then brush them, and finally rinse them again. Take eight new filter pads and insert them as directed in method of assembly instructions. e. Care and Maintenance After it has been used the filter should be dismantled, washed, and thoroughly dried. The strainer should be unscrewed, cleaned and reconnected. As soon as the parts are completely dry the filter should be reassembled without filter pads, the outer edges of the screens and frames covered with a thin layer of grease, and the canvas cover replaced.

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