The description and operation of this filter is given as follows:

"These filters are 6 1/2 feet in diameter, 13 feet high; are of wrought iron and steel. All the parts are perfectly adjusted and easy to operate.

Fig. 13.   The Hyatt Filter

Fig. 13. - The Hyatt Filter.

They are especially adapted to large hotels, mills, factories, pumping stations and industries requiring an abundant supply of pure water. They are filled with about 156 bushels of filtering material, two parts coke and three parts sand, all carefully sifted.

"To Filter. - Open inlet valves A and B and outlet valve C, all other valves being closed. Water then enters the filter above the filtering material, percolates down through it and passes through the outlet cone valves, which prevent the escape of the sand, while the water passes readily through them into the outlet pipe X.

"When Washing. - Close the inlet valve A and outlet valve C, remove the clamp and ball valves from the discharge valves E, E, E, E at the top of the filter. Then open the valve L on the pipe connecting the inlet and outlet pipes. Water then passes from the inlet to the outlet pipe, thence through the cone valves K and up through the filtering material, loosening it and producing pressure, which causes the material to be discharged through the discharge pipes into the tank or upper compartment, which should always be kept full of water. The filtering material being heavy settles immediately to the bottom of the tank, displacing the water, which flows out through the upper waste pipe G, carrying with it the silt and other impurities that have been arrested by the filter bed since the last washing.

"When the filtering material has all been discharged into the tank, close the valve L on the pipe connecting the outlet and inlet pipes, open lower waste valve H, and also raise the centre valve, F, by means of the hand wheel V at the top of the filter; this will allow the filtering material in the upper compartment to settle back into the lower compartment, and at the same time subjects it to a second washing, the falling material displacing the water, which flows off through the lower waste pipe H, carrying with it any impurities not removed by the first washing in the upper compartment.

"After the filtering material has all settled back into the lower compartment, wash off the seat of the centre valve F, by means of a hose, which should be fastened on to the end of the 1 1/4 inch pipe R, care being taken to have the seat free from sand. Then replace clamp and ball valves, E, E, E, E, close the lower waste valve H, and the filter is ready for work.

"The first filtered water should be used to fill the upper compartment, as it will not be perfectly bright. This is done by opening the valve on inlet pipe A, and the valve J on pipe extending from outlet to tank. After tank has been filled close last-mentioned valve and open valve C on outlet pipe, and bright filtered water will be obtained.

"If, in discharging the filtering material a discharge pipe becomes clogged, a passage may be opened by means of the wrought-iron loosening rods S, the ends of which project above the cover of the stuffing box on the discharge valves. To use the rods turn them around by means of a wrench.

"The coagulating apparatus is connected with the main supply pipe by means of two 1/4-inch brass pipes, which are tapped into the main supply pipe at either side of the gate valve B. The inlet pipe to the coagulating apparatus extends through the cover; the outlet pipe extends nearly to the bottom of the apparatus. In each pipe, between the supply pipe and the apparatus, globe valves N and M are placed; also unions are placed between globe valves and apparatus. The object is to permit the coagulating apparatus to be removed, if necessary, without disturbing the main piping.

"The flow of the coagulant depends upon and is regulated by the difference of pressure at the points where the inlet and outlet pipes, to and from the apparatus, enter the main supply pipe. This difference of pressure is produced by partially closing the gate valve B. A difference of pressure between these two points of 1/4 to 1 pound, usually about 1/2 pound, will be sufficient. The globe valve N on the inlet pipe should always be kept wide open. All further regulation of the flow of the coagulant should be done by means of the globe valve M on the outlet pipe from the coagulating apparatus.

"To fill the'coagulating apparatus close the globe valves M and N and remove the plug 0 in the cover of the apparatus. Draw out all solution in the apparatus through the waste pipe P. Put in about nine pounds of ammonia alum (crystal or lump), fill the interstices with the solution taken out, and replace plug 0. As little coagulant should be used as will do the work properly. One to two grains of alum to each gallon of water is about right.

"In case the orifices of inlet and outlet pipes of apparatus become obstructed, close the gate valve A and open valves M and N and valve in waste pipe P. The orifices will be freed by means of the strong current thus produced through the inlet and outlet pipes of apparatus.

"The coagulant used is the cheapest and most effective known, and is entirely removed by filtration. The highest authorities agree that sulphate of alumina, on account of its cheapness and efficiency, is the most practical of all known coagulants.

"The aerating system described on another page, applied to large plants, is economical and perfect in its operations, acts by gravity, entails no loss of head or of power, and combines twenty-five per cent, or more of atmospheric air with the water under static pressure, oxidizing the impurities, destroying the conditions of germ propagation, and so regenerating the water that it will keep sweet much longer in pipes or reservoirs than water not so treated".

Its action, briefly stated, is this: It changes into tangible form the impurities in solution, and gathers together these and the exceedingly fine particles of clay, so that they are filtered out and removed with the impurities. "The moment it is diffused through the water it completely disintegrates, and its elements unite with others, always found in water, forming new and more permanent attachments. Thus its own form and the forms of all the impurities with which its separated elements come in contact are changed. They instantly flock together, a hundred or a thousand particles into one, and then, as the water passes through the filter, they are removed altogether"

The capacity of this filter depends upon its size. Arrangements for the purification of any quantity of water can be made.