Copyright Goodheart-Willcox Co., Inc. 110 Section 1 Introduction to Plumbing Unlike US customary measure, where dimensions are often expressed in both feet and inches (2′-3″), the metric system does not mix its units. A distance of 2 meters and 3 centimeters, for example, is written as 2.03 m or 203 cm, never as 2 m-3 cm. Common metric units used in plumbing are: ■ ■■ Meters for long distances. ■■ Centimeter for short distances. ■ Millimeter for small measurements, found in some pipe diameters and nut sizes. ■ ■■ Liter or cubic centimeter (cm3) for liquid volume. ■■ Cubic meter (m3) for dry volume. ■ Pascal for pressure. One Pascal is equal to one newton per square meter. The newton is the metric unit for force. A newton is the amount of force needed to accelerate a weight of one kilogram one meter per second. ■ ■ Degrees Kelvin or degrees Celsius for temperature. The degree Celsius is equal to 14/5 Fahrenheit degree. Kelvin is in the Celsius scale and measures temperatures in the super-cold range (–273° and up). Figure 6-27 illustrates comparative dry volume mea- surements and provides factors for converting between the US customary and metric systems. The comparison of liquid measurements in the customary and metric systems is shown in Figure 6-28. The Kelvin (absolute) or the Celsius scale is eas- ier to understand if seen with the familiar Fahrenheit. Figure 6-29 shows how temperatures from one scale can be converted to a like temperature on other scales. Goodheart-Willcox Publisher Figure 6-26. Comparison of relative lengths of metric and customary units. Meter Yard Foot Decimeter Inch Inch Actual Centimeter Actual Millimeter Actual US Customary and Metric Equivalents Example 1˝ = 25.40 mm 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 by 2.54 16˝ = 16 × 2.54 = 40.64 cm 1′ = 0.3048 m To convert feet to meters, multiply by 0.3048 3′ = 3 × 0.3048 = 0.9144 m Polymetric Services, Inc., Tarzana, CA 91356 Figure 6-27. Metric and customary dry volume measurements and conversion factors. Cubic inch Cubic centimeter Cubic foot Cubic decimeter To convert from cubic inches to: Multiply by: Example: Gallons Cubic feet Liters 0.004 0.00058 0.016 3674 cu in = ____ gal. 4677 cu in = ____ cu ft 286 cu in = ____ liters 3674 × .004 = 14.7 gal. 4677 × .00058 = 2.712 cu ft 286 × .016 = 4.576 liters To convert from cubic feet to: Multiply by: Example: Gallons Cubic inches Liters Cubic meters Cubic yards 7.48 1728.0 28.32 0.028 0.037 6.5 cu ft = ____ gal. 3 cu ft = ____ cu ft 1.5 cu ft = ____ liters 278 cu ft = ____ cu meters 5687 cu ft = ____ cu yards 6.5 × 7.48 = 48.62 gal. 3 × 1728.0 = 5184.0 cu in 1.5 × 28.32 = 42.48 liters 278 × .028 = 7.784 cu meters 5687 × .037 = 210.42 cu yards