THE WATERWORKS

Southland Times, Issue 20793, 6 June 1929, Page 6

THE WATERWORKS

DOWN THE WELLS

INTERESTING TOUR OF INSPECTION

PRINCIPLES EXPLAINED

Though much has been said and written about Invercargill’s waterworks there are few people who know anything more about them than their locality and external appearance. A more intimate knowledge can be acquired only by descending the wells and inspecting the headworks in the company of an engineer, and this was what a Times reporter did yesterday, his guide being the Town Engineer, Mr F. M. Corkill. “Before we go to the waterworks,” said Mr Corkill, “let me show you how our water is being wasted.” He took the reporter to a lavatory in rear of one of .the banks and there water was running to waste at the rate of 1500 gallons an hour. “This is going on all over the town, but we are doing our best to put a stop to it by sending notices to offenders; If they fail to rectify matters the Corporation will prosecute them.”

The Press representatives had been warned to wear old clothes, but the task before them required greater precautions than this, for Mr Corkill produced dungarees, gum boots and a superannuated, hat. “You’ll need them,” was his warning of the dirty depths to which the descent was to be made.

The compressor house was visited first. Here four air compressors are situated, each being driven by an electric motor. These compressors supply compressed air to the various bores. The air pressure from each is dependent on the depth of the bore which it is supplying. Two of the compressors were seen at. work, one at a pressure of 351bs to the square inch, the other at. 751bs. The compressed air is delivered into the well down an air-pipe. No. 2 Bore. A descent was then made down a timber lined shaft thirty feet deep. This brought the party down to the top of the actual bore which is a 22-inch diameter steel cylinder driven through gravel to a depth of 140 feet below ground level. Water coidd be seen glistening deep down the bore. The engineer tried the depth with the sounding line which is used every morning to test the depth of water. Yesterday water was encountered 57ft 4in from the top of the bore. Inside the well there is a 7-inch diameter pipe up which the water comes. Inside this pipe again is a smaller pipe 21 inches in diameter down which the compressed air is delivered from the compressor. This pipe is quite hot to the touch as air when compressed rises in temperature. The water from No. 2 bore is not raised right to the surface. There are several factors determining how high the water can be effectively pumped and in compliance with the principles of hydrostatics the water from No. 2 bore is pumped to a certain height and is then taken through a tunnel to connect with the supply from No-. 1 bore. The combined supply from these bores is then raised by a centrifugal pump.

The arrangement seen in the bore constitutes an “air-lift.” The compressed air delivered through the air-pipe end through fine apertures forms an intimate mixture, frothy in appearance, with the water inside the 7-inch riser pipe. This mixture being lighter than water is forced to rise by the pressure of the surrounding body of water in the well. This method of pumping is a very convenient way of dealing with small diameter pipes and deep wells as the cost of installation is comparatively trifling. There are no expensive pumps and no moving parts. At the same time they are not mechanically as efficient as modern pumps, but at the waterworks, as in many other places, efficiency has (o give place to convenience. No. 1 Bore. No. 1 bore was next inspected. Acrobats, sailors and engineers may enjoy descending small perpendicular ladders for sixty feet, but reporters aspire to higher things. That, at any rate, was how one Press representative felt as he felt for rung after rung below him. But. the descent, of the well was only the beginning of troubles. A fearsome trip through a cavity of night had to be undertaken. This cavity was in actual fact the tunnel connecting No. 2 bore with No. 1. Water flowed along the tunnel at a great pace. It also began to flow through one of the reporter’s gum boots, making him realize that taps and cisterns were not the only things controlled by the Corporation which leaked. An old tunnel coming from the original well in the waterworks building could be seen but along this the party did not venture. An occasional dam in the tunnel between bores one and two provided some excellent hurdling’ practice for members of the party, with the prospect of an icy douche if a mistake were made. On returning to the platform above the well of No. 1 bore the engineer instructed that the pump for the bore should be started up. When this was done the water was seen flowing from the end of the riser pipe into the tunnel coming from No. 2 bore. The water then flowed into the well from which it was sucked up the pipe to the reservoir. The ascent of another stage brought the party to where the suction pump is situated. This delivers about 10,000 gallons an hour to the surface reservoir. Opposite the pump was the stand for a similar pump which is at present being used elsewhere but which will shortly be replaced. When at the surface again the reporter saw the pipe delivering the water from the two bores into the reservoir. From the pipe the water goes through a gauging box before actually entering the reservoir. This gauging box has a measuring device. A simple calculation with the use of a formula enables one to tell how much water is entering the reservoir at any time. When the reporter was present 11,370 gallons ah hour were flowing in. There are five reservoirs at the works, this representing a reserve supply of 14 days. During storage the water is -aerated and a gbod deal of the iron, which is the onlyunsatisfactory feature of the water, settles through the action of the air. The water from the reservoir runs into the suction well for the tower pumps. Three pumps, electrically driven, then deliver it into the tower. An indicator on the tower shows how much water there is in the tower tank at any time. It was only two feet from being full yesterday when seen. Bores 4 and 5. Number five bore, which is situated on the south-western corner of the reserve, was inspected briefly. It delivers about 13,000 gallons an hour. In this bore the water is pumped right to the surface into a tank and then runs into reservoir number 4. Number four bore is outside the reserve among the trees west of Elies road. Here men were at work re-installing the Boving pump which has been undergoing repairs. A descent of 50 feet was made to the 22inch diameter well which penetrates another 90 feet. The Boving pump is located at the bottom of the 50 feet shaft. There is also an air lift in this well with a 6-inch riser pipe and a 2 4-inch compressed air pipe as in the other bores.