USE OF FLUSH-TANKS 231 



These postals were sent to those cities of between 10,000 

 and 60,000 population, in the New England and Middle Atlantic 

 States especially, which were reported in the " Manual of 

 American Water- works " for 1897 as having separate or sani- 

 tary sewers. Eighty answers were received, and the courtesy 

 and good- will expressed in all was much appreciated. It was 

 the same story in nearly all cases. " I would be pleased to 

 answer your questions fully, but this is the best that I can do 

 for you," or " This is only my idea, while I can readily under- 

 stand that what you want is the result of actual experience," 

 or " I cannot give you the desired information, but would be 

 thankful to you if you would let me know the result of your 

 inquiry." The results given below in a brief summary show 

 chiefly how uncertain and vague is the knowledge on the sub- 

 ject, and how necessary are some experiments and investi- 

 gations. 



Of the eighty engineers who sent replies to question No. i, 

 whether flush-tanks are necessary, seventeen had no opinion 

 on the subject; twelve had experience only with combined 

 systems, but had, according to their replies, found no trouble 

 in keeping the ends of their 10- and 12 -inch laterals clean with 

 rain or with hand-flushing; twenty-six of the eighty used 

 periodic hand-flushing and found it to answer every purpose ; 

 keeping the sewers clean and free from obstructions; twenty- 

 five either used flush-tanks or considered them a necessity for 

 small pipe sewers. It was not possible in these last answers to 

 separate actual experience from personal conjecture on the 

 question, so that this number may include many hearsay 

 opinions. 



The evidence is not very clear. The fact that twenty- 

 six used hand-flushing satisfactorily indicates that such flush- 

 ing is sufficient. That it must be properly and regularly done, 

 however, is made plain by the fact that, out of twenty-five 

 believing in flush-tanks, nine had tried periodic hand-flushing, 

 found it uncertain and irregular, and had put in flush-tanks, 

 to secure proper attention. On the other hand, of the twenty- 



