46 
BULLETIN 304, U. S. DEPARTMENT OF AGRICULTURE. 
Practice is not uniform as to the best method of preventing water 
from flowing back through the pipes into the district from the river 
when the pumps are not operating. Some prefer to carry the dis- 
O 
Boile 
Bo/ler & Fuel Room / 
\ 
... Y-'-'vn — fpB — .. 
50" Discharge Pijpe\\ 
chiri — tirrj 'ecu 
Concrefe 
Supports for Discharge Pipe 
•u=a- — it 
^4 
£.'e*37 
/ t\>- r r?cur>c/P/7ej lL.j\«__J ! £fev.2 3 
Fig 2.— Plan and elevation of pumping plant, Louisa-Des Moines Drainage District No. 4, Iowa. 
charge pipe through the levee above high water and then down, with 
its end opening below low-water line, so as to secure a water seal. 
This is necessary in order that the pipe may act as a siphon and that 
