How to Figure the Weight of Water Inside Piping
You can calculate the weight of water contained in plumbing with a few simple formulas to estimate the volume of a pipe. Due to differences in pipe fittings, the answer obtained will be slightly imprecise, but accurate enough for planning purposes.
When planning pipe support strategies, consider the weight of the pipe and fittings. which can be significant compared to the water. Also add a safety margin to account for dynamic loads placed on the pipes when water flow is abruptly turned on or off.
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Things You'll Need
- Tape Measure
- Pencil and Paper
- Calculator
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Instructions
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1
Measure the length of the pipe with a tape measure and record the result. Also record the diameter (width at the widest point) of each length of pipe measured.
If the pipe has elbows, tees or other fittings, approximate the total pipe length by adding the length of each fitting to its associated pipe.
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2
Sum the total length of each pipe diameter present.
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3
Convert the total lengths into inches by multiplying the number of feet by 12.
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4
Calculate the total volume of each pipe diameter present.
Volume = (Diameter/2)squared x pi x length
Example: Ten total feet (120 inches) of four inch diameter pipe
Volume = (4 inches/2)^2 x 3.14 x 120
Volume = (2)^2 x 3.14 x 120
Volume = 4 x 3.14 x 120 = 1507 cubic inches -
5
Add the total volumes from Step 4 together.
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6
Multiply the result of step 5 by 0.036, the weight in pounds of one cubic inch of water.
Example: 1507 cubic inches of water x 0.036 pounds/cubic inch
= 54.2 pounds of water
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Tips & Warnings
Hot water (100F) is about 1% lighter than cold water.
Pi (п) is a mathematical constant always equal to 3.14.
Squaring (^2) is accomplished by multiplying a number by itself.
To obtain slightly more accurate results, perform the calculations with the inside rather than outside diameter of the pipe. Inside diameter can be obtained by measuring an uninstalled sample of the pipe, or estimating the thickness of the pipe walls and subtracting it from the outside diameter.
