WATER 13 



water. Storage alone, however, does not entirely eliminate the 

 micro-organisms. 



If pathogenic bacteria gain entrance to pure water, that is water 

 free from such organisms as naturally feed on them, up to a 

 certain point they multiply more rapidly than in impure water. 



Turbid water becomes clarified by storing so that its general 

 appearance is improved, but peaty waters retain some of their 

 colour. Storage also reduces the hardness and the amount of free 

 and saline ammonia. 



In impounding reservoirs there is always some vegetable growth 

 where the water is comparatively shallow and where light can pene- 

 trate. This, as it decays, adds vegetable organic matter to the 

 water, which is undesirable. 



In the deeper parts where light cannot penetrate there is no 

 floral life, and it is for this reason that the sides of storage reservoirs 

 are made practically vertical. In service reservoirs there is no rise 

 and fall in the depth of the water as is the case with impounding 

 'reservoirs, so that there is less opportunity for plant growth. 



With both impounding and storage reservoirs precautions are 

 taken to prevent the entrance of sewage and waste drainage. 



Storage of Domestic Supplies. With the possible exception of 

 houses and premises provided with a constant supply of water 

 direct from the main, some provision is necessary for the storage 

 of a sufficient quantity of water to ensure that there will not be 

 a temporary shortage. Storage cisterns may be of galvanised iron, 

 lead or slate. Lead is unsuitable where the water has a lead-solvent 

 or lead-erosive action. Slate is a good material, but it is difficult 

 to make satisfactory joints. 



Whatever type of cistern is used the water should be run off if 

 it has been in the tank for any length of time. Cisterns should be 

 placed so that there is convenient access to them, and they should 

 be inspected periodically. They should be covered over to prevent 

 the entrance of vermin and dirt, and they should be ventilated. 



When a cistern is cleaned out, the lead or zinc surface should 

 not be scrubbed as this removes the protective coating. 



On farms not receiving public water a supply is often pumped 

 up from a deep well by a wind-driven force pump and conveyed 

 to the farmhouse cistern, and to one or more tanks situated at 

 convenient centres for distribution. These tanks act as feeders to 

 drinking-troughs distributed about the farm, such as in the cattle 

 courts, stable-yard, &c. They are fitted with ball-cocks, and are 

 self-filling from the main feed tank. The ball-cock should be built 

 into the wall or so covered over that the water will not get frozen in 



