INVESTIGATION OF DRINKING WATER SUPPLIES 167 
of interest to enumerate some of the most common errors that 
are found associated with water supplies. The errors referred 
to are briefly summarized as follows: 
1) The use of surface waters without treatment, as all 
such waters must be considered open to contamination. The 
sanitary policing of such sources is- usually impossible or im- 
practical. 
2) The installation of water purification plants in localities 
where underground supplies were available and would have 
provided a safer source. 
3) The installation of water purification plants by local 
authorities who have little or no understanding of the theoreti- 
eal and practical side of the treatment nor the difficulties 
attending the operation of these plants. Many such plants 
have been installed and the authorities believed them to be 
equipped with automatic devices which would insure an ef- 
fluent of good sanitary quality. This impression is erroneous 
since these plants require the most careful attention by trained 
operators at all times during the operation. 
4) The installation of hypochlorite or liquid chlorine plants 
to purify water that cannot be properly purified by these 
chemicals bécause filtration is required to render it suitable for 
such treatment. 
5) The addition of hypochlorite or liquid chlorine to raw 
water as it enters a filtration plant rather than to the effluent. 
This practice often makes very difficult the administration of 
these chemicals in proper amounts. 
6) The failure to keep on hand duplicate parts of im- 
portant equipment, especially parts of chlorine apparatus that 
are likely to get out of repair. The lack of such parts may 
make it necessary to allow untreated water to be discharged 
into the distribution system. 
7) The installation of by-passes around water purification 
plants by which untreated water can be admitted into the 
system, without passing through the plants. 
8) The improper operation of water purification plants 
by unskilled or inefficient operators. 
