CISTERNS AND HOUSE TANKS 145 



they are built near or even under a house, dairy or barn the 

 water may often be pumped directly from them to the sink or to 

 the dairy or watering trough. 



Because of their shallovvness and the smoothness of their walls 

 cisterns can be much more quickly and thoroughly cleaned than 

 wells. Consequently they are usually cleaned more frequently 

 and the water is kept in better condition. 



Disadvantages of Cisterns. Cisterns, notwithstanding their 

 many good qualities, have some disadvantages. The dirt from 

 the roofs is very objectionable, including dust blown from barn- 

 yards and highways, the droppings of birds, etc. The remedy is, 

 as already stated, to allow only that portion of the water falling 

 during the latter part of a shower, after the dirt from the roof has 

 been largely removed, to enter the cistern. 



Inasmuch as the cistern has to be emptied of its water before 

 it can be cleaned, there must be some other available supply to 

 tide over until it shall be again filled by the rains, but this dis- 

 advantage, of course, applies equally to wells. 



The greatest disadvantage of a cistern and one which subjects 

 the users to grave danger is the liability to crack. No matter how 

 good the cement used in the construction or how careful the 

 workmanship, cracks are liable to develop and admit shallow and 

 possibly polluted ground waters. It is to the waters entering in 

 this way that the notable hardness often indicated in cistern waters 

 is due. Cistern water under normal conditions is soft, and if it 

 becomes hard it is a sure indication that ground water has in some 

 way found access to the cistern. It is a danger signal which 

 should not be disregarded, and whenever it is noted the cistern 

 should be emptied and repaired at once. 



Size of Cistern Required. --The ordinary cistern, usually 5 or 

 6 feet in width and 10 or 12 feet deep, almost invariably fails to 

 meet the demands on it during extended periods of drought. To 

 insure a supply which can always be depended on either for do- 

 mestic or for stock use, much larger cisterns or one or more re- 

 serve cisterns are necessary. 



