6 BULLETIN 57, U. S. DEPAETMENT OF AGRICULTURE. 



The above treatment will, in a large iiieasui'e, purify surface 

 water for household uses other than drinking or cooking; but if this 

 water is to be used for drinking or cookmg it should first be boiled. 



DISTILLED WATER. 



Sometimes a simple still can be conveniently used on a kitchen 

 range to provide distilled water for drinking purposes. SaHne (alkaH) 

 waters are satisfactorily treated in this way. Figure 4 illustrates a 

 form of stni which has been found effective and convenient for house- 

 hold use.^ It has the advantage of bemg inexpensive and can be made 

 by any tinner. The still consists essentially of a water boiler (A) on 

 the range, having a capacity of about 1^ to 2 gallons, and a condenser 

 suspended at the proper height from the ceiling. The. pipe (B) con- 

 veys steam to the condensing chamber (C) and is kept cool by water 

 in the compartment (Z>). The distilled water collects m (E) and can 

 be drawn off from time to time or allowed to run continuously into the 

 bucket (F). The metal used in the construction of the still should 

 be well-tinned copper and no solder should be exposed to the action 

 of either the steam or the distilled water. 



UNDERGROUND WATER SUPPLIES. 



CONTAMINATION. 



It is usual to distinguish between shallow underground suppUes and 

 deep underground supphes. Wells from 15 to 30 feet in depth to 

 water flowing in a layer of gravel or sand, which rests on an impervious 

 stratum, are considered as sources of shallow underground supply. 



Both shallow and deep farm weUs are often polluted from local 

 sources. They are often located for convenience in the barnyard, 

 under the barn or stable, close to stock pens, privy vaults, or leaching 

 cesspools, or close to the back door, out of which household slops are 

 thro^\^l and near which animal and vegetable refuse is often allowed 

 to accumulate and decompose. The soil surrounding the well becomes 

 saturated with organic filth and, unable finally to perform its useful 

 work of filtration and purification, allows the surface water percolating 

 through it to carry its load of contamination into the well. 



The curbing or covering is often loosely constructed of boards, 

 permitting small animals and vermin to fall into the well; and 

 surface water carrying fiJth and manure, especially after rains, runs 

 into the well from the top. 



The well may be located at such a distance from sources of con- 

 tamination that ordinary pumping \\dll bring no bad results, but in 

 case of unusually heavy pumping the underground water surface for 

 a distance around the well may be sufficiently lowered to reach the 

 zone of contamination. This principle is illustrated in figure 5. 



» Montana Sta. Giro. 7. 



