It is interesting to realize that nearly every fine home in New York, especially on Fifth Avenue, has a filter, despite the city’s excellent water supply. Not so much to save life, as it so often does owing to frequent invasions of germs into even excellent water, but for the feeling of clean unflavored, unfishy, unwoody water and for the insurance of long life of the plumbing system--and to save deterioration in plumbing is a thing devoutly to be wished. Sand or quartz is the usual medium for filtration in the home. Bone char is often added to these to destroy taste, for there is nothing as disagreeable as water with a decided taste. There are a few filters to-day which when installed in the cellar consist of one or two vertical tanks attached to the water supply. In one tank is quartz through which the water passes and in the other is bone char to carry away flavor. In one case the filter has a simple lever which when set at a certain spot on the dial washes out the filter beds and frees them from contamination. As the impurities in the water are removed by a filter they accumulate in a mass or cake on top of the filter bed. If this cake or matted formation is not broken up and thoroughly disintegrated, it will roll up during the washing process and not only clog but contaminate a filter bed, utterly destroying its efficiency as a purifying medium, steadily diminishing the water supply. Hence a cutting plate is placed immediately above the bed of quartz. As soon as the operating lever is moved to the point “Washing,” the washing current is introduced at the bottom of the filter, the filter bed is lifted bodily upward and forced through the cutter, which literally tears the matted film of impurities into fragments. At the same time it thoroughly breaks up the bed, separates and perfectly scours each grain of filtering material, by the force of the reverse current of water in a space twice the size it occupies during the filtering process. The impurities having been separated from the bed and broken up into minute particles are carried out of the filter through the waste pipe by the reverse current of water. During this process a screen at the top of the filter prevents the filtering material quartz from escaping out of the filter. In this way by the least effort--the turn of a handle--once a week--the filter becomes a boon and not a menace. After the cleaning process is over, a matter of from ten to twenty minutes, the lever is turned to another point “designated in the bond” and the filter goes back to normal. The agitated sand and char are calmed down and ready to chasten the next lot of water.