124 AXTOFAGASTA RAILWAY WATERWORKS. 



The main pipt' lines are as follows : — 



The three first mentioned pipe lines deliver their waters 

 to the storage reservoirs in San Pedro. From these the No. 1 

 and No. 2 mains are fed. 



A section of the pipe lines from San Pedro to Antofagasta, 

 and, indeed, from the intakes at Polapi and Siioli shows a con- 

 tinuous fall, without a reverse grade at any point. This is a 

 remarkable feature of the main pjpe line system, and in order 

 to obtain pressure in the mains, inverted U legged standpipes 

 have been fixed in the main, to enable the various supplies to 

 be given and to avoid having to limit main valves. 



The first main laid from San Pedro to Antofagasta was of cast 

 iron pipe of French manufacture, with a joint known as the 

 " acme " joint. This consists of a short socket with outside 

 lugs for bolts. The spigot end carrying a rubber ring of square 

 section is inserted, and a cast iron packing gland is bolted down 

 on to the rubber ring expanding the same into a groove on the 

 inside of the socket and making the joint water-tight. 



This type of joint in the No. 1 main has rendered good ser- 

 vice, and joints, which from various causes have been taken out, 

 show very little deterioration. At the same time it must be borne 

 in mind that the main is worked under very little pressure. On 

 occasions when, by accident or mal-intentioned workmen in the 

 nitrate district, a main valve has been closed, the joint has failed 

 to stand where an ordinary leaded joint has not suffered. 



The projecting lugs for the bolts on the socket end of the 

 pipe are also a weak point, as with the rough handling almost un- 

 avoidable where sea transport comes into question, they are often 

 broken off. 



In order to limit the maximum head, the pipe lines are divided 

 into sections varying in length, but with a maximum ruling head 

 on the sections of 150 metres, At the end of each section a relief 

 or break pressure tank, circular in plan, has been placed. This 

 tank is constructed of riveted steel plates and has a diameter 



