168 UNIVERSITY OF WISCONSIN STUDIES 
9) The location of wells, pumping apparatus, exposed 
suction mains, reservoirs and filters where they will be subject 
to flooding with surface water. 
10) The improper construction of well casings and covers, 
and the lack of adequate provision for surface drainage to 
prevent pollution of the well with surface water. 
11) The construction of pits around wells at the surface 
in which all or a part of the pumping equipment is located. 
This applies especially to drilled wells. It is difficult to pre- 
vent surface and waste water from collecting in such pits. 
12) The connection of any part of the system with sewers 
which makes it possible for sewage to back up into wells, well 
pits, storage reservoirs, etc. 
13) The improper construction of underground and sur- 
face reservoirs. This includes structures that are not water- 
tight, those where the covers admit surface water and others 
where the clean-outs are connected with sewers or bodies of 
polluted water, the surface of which may be raised to an eleva- 
tion higher than the bottom of the reservoir. 
14) The installation of emergency connections which may 
permit untreated surface water, or water of unknown or ques- 
tionable sanitary quality, to be admitted to the system. There 
should be a complete physical separation between water sup- 
plies that are safe and those that are known to be unsafe from 
a sanitary point of view. 
Many of thege defects have been the cause of epidemics of 
water-borne diseases, consequently, their sanitary significance 
is at once apparent. These errors can be prevented in new 
supplies and corrected in existing supplies by proper health 
administration carried out by trained workers who have the 
proper facilities to put such supervision into effect. 
CONCLUSION 
The purpose of this article is to draw the attention of 
health authorities and others to the importance of thorough 
investigation work when the safety of a water supply is to be 
determined from a sanitary point of view. The investigation 
should be undertaken by trained workers who understand the 
