10 Rule of Thumb

Question 1

Flow Rate

Answer 1

200gpm for 1in
For every 1/8in diameter change, add or subtract 50gpm For every 1/4in diameter change, add or subtract 100pgm.

Question 2

Nozzle Size / GPM

Answer 2

3/4in / 100gpm
7/8in / 150gpm
1in / 200gpm
1 1/8in / 250gpm
1 1/4in / 300gpm
1 1/2in / 350gpm

Question 3

Hand Method (2 1/2in)

Answer 3

Works for flows of 100 to 500 gpm, primarily for 2 1/2in hose.
- Base of finger is gpm in 100s (100, 200, etc)
- In between is half hundreds (150, 250, etc).
- Tips of fingers odd numbers (start at 3)
- In between fingers, even numbers (start at 4)
Divide gpm (base of finger) by 100. Multiple that new number by tip of finger.

Question 4

Hand Method (1 3/4in)

Answer 4

Done the same way as 2 1/2in but numbers are different.
- Method is good for 100-200 gpm flow rates
- Tips labelled 1 to 5
- Tips also labelled 100, 125, 150, 175, 200gpm
- Middle/base of fingers labeled 12
Find the gpm flow rate (100gpm, 125gpm, etc) and find the corresponding number at the tip of finger (index finger is 125gpm and #2). Multiply the number at the tip by 12.
That would be your FL for 100ft section of 1 3/4in hose

Question 5

Drop 10 Method

Answer 5

Only works for 2 1/2in
- Take gpm and drop last digit
- Subtract 10 from that number
- That is FL for 100ft of 2 1/2 in.

Question 6

Rule of Thumb for Determining Available Residual Pressure (p. 202)

Answer 6

I can’t figure out how to write this one. Look in the book. Probably won’t be on the test… Maybe it will. I don’t know.