STORAGE AND DISTRIBUTION. 149 



Having now discussed most of the forms of filters 

 and tanks which would find place in a small water 

 supply scheme for purifying and storing water, we 

 proceed to investigate how the distribution to the 

 various parts of the grounds and house is effected. 

 Outside the house cast-iron pipes are invariably used. 

 They may be had in various sizes. Those which prin- 

 cipally concern the reader are 6, 5, 4, and 3 in. pipes. 

 Two and ii in. mains are made, but they are not 

 really very satisfactory. The other sizes and larger 

 can usually be had from good makers, cast vertically 

 in dry sand, and a much sounder pipe will result. 

 It pays to go to a reliable firm. The pipes are cast 

 in 6 ft. or 9 ft. lengths, according to size, and must be 

 coated with Angus Smith's solution inside and out. 

 This solution is composed of coal-tar and pitch-oil 

 in the proportion of one part of tar to three of oil. 

 The mixture is heated to the boiling temperature of 

 the oil and the castings are immersed in it and al- 

 lowed to remain until the temperature is diffused 

 throughout the mass. The pipes are then gently 

 withdrawn, the naphtha and other volatile oils evapor- 

 ating and drawing off the iron, so that while still 

 very hot a firm hard coating of pitch is left which 

 firmly adheres to the pipe. It requires care in doing 

 however, because the heat of the mixture must be be- 

 tween 350 and 450 Fah. ; if it is too hot the pitch 

 will scale off. The flange joint for pipes used in 

 pump sections has been discussed. For distribution 

 two forms of joint are employed. 



The ordinary spigot and socket form is most usually 

 employed, as shown in section in fig. 117. The pipes 

 are fitted home, and into the intervening space be- 



