Where the water can be supplied by gravitation, and the tanks can be placed at a sufficient elevation to command the service cistern, no pumps are required, the softening process, in fact, in no way necessitating pumping. The space occupied by the whole of the tanks and apparatus is 60 ft. square, 3,600 ft. area, and softens 50,000 gallons per day. For the daily softening of quantities less than 1,000 gallons, the tanks are made of galvanized sheet iron, and the whole apparatus and tanks are self-contained, so as only to require the making of the necessary connections with the existing supply and delivery pipes, and fixing in place. No expensive foundations are required, and the entire cost of an apparatus--see Figs. 2, 3, 4, 5, and 6--capable of softening 500 gallons per day is about £75. Annexed is a more detailed description of the manner of fixing and working the smaller apparatus.
The tank must, of course, be set up perfectly level. The pipe from the source of supply--in the present case from the hydraulic ram--must be attached to the upper three way cock at A, on the accompanying engravings, and the pipe to supply softened water is to be connected to the lower three-way cock at B, and should be led into the elevated cistern with a ball cock so as to keep it always filled. The three ball cocks in C, D, and E should be adjusted to allow the tanks to fill to within 3 in. of the top. The nuts at the upper extremity of the three rods, F, G, and H, should be so adjusted that when the water in the several tanks has been drawn down to within 15 in. of the bottom the rocking shaft, I I, is drawn down and the vertical rod, J, lifted so as to allow the wheel, K, and spindle, L, to revolve by the action of the weight, M. The length of the chain is such that when the weight, M, rests upon the floor the face of the raised rim on the wheel, K, should not quite touch the rod, J, and if necessary, a thin packing should be put for the weight to drop upon.
The lime to be used should be pure chalk lime free from clay, mixed with water to a smooth, creamy consistency, and then poured into the small tank, N. This tank should then be filled with water to within 3 in. of the top, and the small air pump worked until the lime has become thoroughly mixed and diffused throughout the water. Care must be taken that previous to filling the tank the float, O, is raised up, as shown by the dotted lines in Fig. 3. After the lime has been thoroughly mixed it should be left for at least eight hours for the superabundant lime to subside, leaving the supernatant fluid a perfectly clear saturated solution of lime. At the end of this time the float, O, should be lowered, so that it may float upon the lime water, and the three-way cock, P, should be turned in such a position as to allow the contents of the tank, N, run into the tank, Q, until the necessary quantity has been supplied, the mode of determining which is hereinafter described.
The spindle, L, should then be turned into the position which allows the water from the source of supply to be discharged into the tank, Q, the float, R, having first been raised into the position shown in Figs. 2 and 5. A second quantity of the lime should now be added to the tank, N, mixed with water, and after agitation, another eight hours allowed for the contents of both the tanks, Q and N, to subside. At the end of this time the three-way cock, P, should be turned through a third of a circle, so as to discharge the lime water into the tank, S; and the spindle, L, should be turned in the contrary direction to the hands of a watch through the third of a circle, so as to allow the water from the source of supply to be discharged into the tank, S, care being taken as before to raise the float, T, out of the water. A third quantity of lime must be added to the tank, N, and now mixed with water to be drawn from the tank, Q, by the tap, U, and after agitation again left for eight hours to subside.
The float, R, may now be lowered into the water in the tank, Q, when it will be found that the clear softened water contained in the tank, Q, will be discharged through the pipe attached to the bottom of the three way tap, B. The weight, M, must now be lifted about 5 in., so as to allow the ring at the end of the chain to be moved back to the next stud on the wheel, K. The lime water in the tank, N, must next be discharged into the tank, V, and then another quantity of lime must be added to the tank, N, and filled up with softened water from the tank, S, by means of the tap, W, and after being duly agitated and left to subside. As soon as the softened water from the tank, Q, has been drawn down to within 15 in. of the bottom, the rod, H, will move the rocking shaft, I, and lift the rod, J, so releasing the wheel, K, and allowing the weight, M, to descend and turn the spindle, L, and the upper and lower three-way cocks through a third of a circle; the effect of which movement will be to continue the supply of softened water from the tank, S, and to fill up the tank, V, with water from the source of supply.
The apparatus will now be in the condition to afford a regular supply of softened water; all that will be necessary to insure its continuous action will be that at certain stated intervals dependent upon the rapidity with which the water is used--but which interval should not be less than eight hours--the following things should be done: (1) The float must be raised out of the tank last emptied. (2) The float must be lowered into the tank last filled. (3) The weight, M, must be raised, and the ring of the chain shifted to the next stud on the wheel, K. (4) The clear lime water found in the tank, N, must be turned into the tank last emptied. (5) The requisite quantity of lime must be put into the tank, N. (6) The requisite quantity of water must be drawn off from the tank last filled into the tank, N. (7) The contents of tank, N, must be thoroughly mixed by means of the air pump. The quantity of lime to be used for each tankful of water must depend upon the hardness of the water, ¾ oz. being required for each tankful for each degree of hardness. It is desirable, however, always to have an excess of lime in the tank, N, so as to insure obtaining a saturated solution of lime.
When first mixed the contents of the tank, N, will have a creamy appearance, but when the superabundant lime has subsided the supernatant liquid will be a perfectly clear saturated solution of lime. Therefore, in the first instance, 3 lb. of lime should be put into the tank, N, and subsequently each time such a quantity of lime should be added as is found to be necessary by the method hereinafter described. The quantity of the saturated lime water to be run into each of the softening tanks, Q, S, and V, will depend upon the hardness of the water. For every degree of temporary hardness a depth of 1-6/10 in. of the contents of the tank, N, will be required; so that if the water has 14 deg. of temporary hardness, then 22½ in. in depth of lime water must be run off into each of the tanks, Q, S, and V. In the first instance an excess of lime may be used, and the softened water tested by means of nitrate of silver in the following manner: A solution of 1 oz. of nitrate of silver in a pint of twice distilled water should be obtained.
Having let two or three drops of this solution fall on the bottom of a white tea cup, slowly add the softened water; then if there be any excess of lime, a yellow color will show itself, and the quantity of lime water used must be reduced until only the faintest trace of color is perceptible.--The Engineer.