and inches (2′-3″), the metric system does not
mix its units. A distance of 2 meters and 3
centimeters, for example, will be written as
2.03 m or 203 cm, never as 2 m-3 cm.
Common metric units that are used in
plumbing are:
• Meter—For long distances.
• Centimeter—For short distances.
• Millimeter—For very small measurements,
such as certain pipe diameters and nut
sizes.
• Liter or the cubic centimeter (cm3)—For
liquid volume.
• Cubic meter (m3)—For dry volume.
• Pascal—For pressure. One Pascal is equal to
Chapter 4 Mathematics for Plumbers
97
Figure 4-25. If a 50-foot horizontal run of building sewer is to be installed, what is the total slope of the run if a
slope of 1¼8 inch per foot is to be established?
Total slope = Slope per foot × feet of run
= 1∕8″ × 50
= 50∕8″
= 61∕4″
50′
Total
slope
Outlet
Flow
Inlet
Line of sight
Builder’s level
or transit
Figure 4-26. The above illustration compares relative lengths of metric and customary units.
Meter
Yard
Foot
Decimeter
Inch
Inch
Actual
Centimeter
Actual
Millimeter
Actual
1″ = 25.40 mm Example:
To convert inches to millimeters, multiply by 25.4 3″ = 3 × 25.4 = 76.2 mm
1″ = 2.54 cm
To convert inches to centimeters, multiply inches by 2.54 16″ = 16 × 2.54 = 40.64 cm
1′ = 0.3048 m
To convert feet to meters, multiply feet by 0.3048 3′ = 3 × 0.3048 = 0.9144 m