This is a sectional view of a Pressure Filter, the letter A showing the curved stone; B represents the charcoal and sand; C, the coupling to be attached to hydrant; D, the water space.

A low pressure filter can be made in a tank with the curved stone cemented at the bottom, this form to be used when no pressure, either from a hydrant or tank above the filter, can be obtained.

Fig. 30.   Sectional View of Natural Stone Pressure Filter

Fig. 30. - Sectional View of Natural Stone Pressure Filter.

The capacity of either of these filters is given at 500 to 1000 gallons per day, according to size and form.

The stoneware filters are adapted where a mechanical filtration of the water is sufficient. They will remove suspended impurities in more or less time.