Usual inclination of pipes.

 1 in. in 12 ft. = minimum fall for house drains; 1 " " 16 " = minimum fall for land drains; 1 " " 40 " = minimum fall for sub-drains for houses; 1 " " 100 " = minimum fall for main drains for houses; 1 " " 150 " =fall of mountain torrents; 1 " " 230 " = " " rivers and rapid currents; 1 " " 280 " = fall of strong currents; 1 " " 340 " = " " ordinary rivers with good current; 1 " " 440 " = fall of winding rivers subject to inundations with slow current; 1 " " 480 " = fall of water channels, supply pipes to reservoirs and small canals; 1 " " 570 " = fall of large canals; 1 " " 1,000 " = very slow current, approaching to stagnant water.

Discharge through pipes.

Discharge in 24 hours divided by 1,440 = discharge per min.; discharge in cubic feet per minute X 9,000 = imperial gallons per day of 24 hours; discharge in cubic feet per minute X 11,000 = U. S. gallons per day of 24 hours; discharge in cubic feet per second X 2.2 = cubic yards per minute; discharge in cubic feet per second X 6.24 =imperial gallons per second; discharge in cubic feet per second X 7.48 = U. S. gallons per second; discharge in cubic feet per second X 133 = cubic yards per hour; discharge in cubic feet per second X 375 = imperial gallons per minute; discharge in cubic feet per second X 450 == U. S. gallons per minute; discharge in cubic feet per second X 2,400 = long tons per day of 24 hours; discharge in cubic feet per second X 2,700 = short tons per day of 24 hours; velocity in feet per second X 0.68= mile per hour; velocity in feet per second X 60 = feet per minute; velocity in feet per second X 20 = yards per minute; pressure head of water in feet = pressure of water in lbs. per square foot X 0.016; pressure of water in lbs. per square foot = head in feet X 62.32.