The volume of the pipe is 0.2078 gallon per foot of length.
I have no idea how much water might be in it.
There need no be any water at all! The capacity of the pipe is 8.11 litres approx.
6.5 gallons, if it is full of water. (if this is a trick question, and the pipe is empty or full of dirt or something, then not 6.5 gallons)
The radius is half of the 4 inch diameter. Therefore, the radius is 2 inches.
Pipe with a Nominal Bore of 4 inch (100mm) Outside Diameter 114.3mm
A "4-inch pipe" means it has a diameter of 4 inches, which makes the radius 2 inches. Did you ever see the formula pi*r^2 for area of circle? The answer is 4pi where pi=3.1416
The volume of water in a 4-inch diameter, 1-foot section of pipe is 0.6528 gallons of water.
100
The volume of the pipe is (pi) x (radius)2 x (length)= (pi) x (2)2 x (120)= 1,507.964 cubic inches = 6.528 gallons (rounded). I have no way of knowing how much water may be in it.
The volume of this pipe is 261.8 cubic feet.
By calculating the areas of circles with diameters 6 and 4 and comparing those: pi3^2=pi9 pi2^2=pi4 pi9/pi4=9/4=2.25 So the 6 inch pipe holds 2.25 times as much as the 4 inch pipe.
111 gallons of water.
There need no be any water at all! The capacity of the pipe is 8.11 litres approx.
6.5 US gallons of water.
Volume = 0.8727 cubic feet OR 1,508 cubic inches.
It is based on the flow area, which is proportional to the square of the diameter. 2 squared = 4. 4 squared = 16. So, the 4 inch pipe can take 16/4 = 4 times the volume of the 2 inch pipe. It might be less confusing if you had picked sizes other than 2 and 4. This is a rough calculation, since pipe inside diameters are not the same as nominal sizes, but close enough for most purposes.
A 4 inch drill pipe torque is used for fishing in small casing.
Probably the wrong size flange. Is the flange a toilet collar? If so the pipe is probably 4 inch.