Calculating Friction Loss
•To calculate the frictions loss multiply the horizontal run by the friction loss per 100 then divide your findings by 100.
•2. Multiply the drop pipe length by the friction loss, then divide that answer by 100.
• Note: To find the friction loss per 100, go to your reference book.  Remember, to check the friction loss, you will need to know:
ØPipe size
ØType of pipe that will be used
ØThe gallons-per-minute (GPM) required