For round cisterns or tanks, the rule is: Area of bottom on inside multiplied by the height, equals cubical capacity. For instance, taking the last tank or cistern in the table: area of 24 inches (diameter) is 452.39, which multiplied by 12 inches (height) gives 5527.6 cubic inches, and this divided by 231 cubic inches in a gallon gives 23 gallons. Fig. [595].
Rule for obtaining the contents of a barrel in gallons. Take the diameter at the bung, then square it, double it, then add square of head diameter; multiply this sum by length of cask, and that product by .2618 which will give volume in cubic inches; this, divided by 231, will give result in gallons.
STRAINERS FOR SUCTION PIPES,
It is very desirable to place an efficient strainer on the suction pipe of a pump where there is the least suspicion that the water contains any sediment or floating matter.
Several of these useful pump attachments have been already shown, connected with pumps, in previous sections of this work, but a few more are here added.
Fig. [597] exhibits a cross section of a strainer of large capacity of long and satisfactory use. It has a semi-cylindrical vessel located in one side of the side pipe. Holes are drilled through the flat side extending across the diameter of the side pipe; any floating matter which will not pass through the holes collects in this strainer vessel and may be easily removed.
Figs. 597 and 598.
Fig. [598] represents a longitudinal section of this strainer. The top of the chamber is covered by a bonnet secured by a claw having one bolt, so that by unscrewing this bolt the claw and bonnet may be unfastened and the settling chamber with perforated plate withdrawn.