The flow rate of water in gallons per minute, or gpm, can be calculated with the help of the Bernoulli equation and careful unit conversion. If the pressure is known in pounds per square inch, or psi, at two locations along the pipe, then the Bernoulli equation can be used to determine the velocity of the water.
You can convert pipe size to gallons per minute of flow by calculating the cross-sectional area of the pipe and making some reasonable assumptions about pipe volume and the rate of flow. Pipe sizing is measured by the internal diameter of the pipe, not the overall outside diameter. Once determined, the overall volume can be calculated.
The psi, or pounds per square inch, is a unit of pressure (P) using the foot-pound-second (FPS) system. To calculate psi, divide the force applied (F) with the area (A). Measure the force applied. Use an instrument such as a force gauge, spring scale or strain gauge. Make sure that the unit is in pounds. Convert the value if necessary.
Fluid pressure at the start of the pipe for gas density calculation based on the ideal gas state equation R - gas constant Gas constant in terms of energy per unit of mass and temperature, for gas density calculation using ideal gas state equation Calculation setup Select value to calculate. You should enter not selected one. D pipe diameter V ...
This equals 15.2 PSI over the 400 feet of pipe, or 3.8 PSI per 100 feet of pipe length. All long-run piping systems must be carefully calculated for pressure losses. Read the pressure-drop flow correlation about 2-inch Schedule 40 PVC plastic pipe from the tabular flow versus pipe-loss data chart.
Calculate the pressure loss per 100 feet of pipe, since this is how published pipe flow data is presented. 135 psi minus 112-psi = 23-psi/350/100 = 6.57-psi drop per 100-feet. As 6.57 psi is less than 6.75 psi, this example lies in the "efficient" realm.
The thread size of the port on your air compressor tank does not determine the pipe size for your piping system. It is calculated with the length of your piping (building size) and air compressor cfm output. Even though the port on your tank may be small, the air is only traveling through a short distance, so the restriction is minimal.
The Hazen-Williams formula is an empirical rule, that holds well for cold water running in pipes under turbulent flow conditions. This is very suitable for situations such as domestic piping and hosing, sprinkler and irrigation systems, etc. For gravitational flow, and for open-channel flow, other calcs are available.
How much water can flow through a pipe (GPM/GPH)? We regularly get asked about the water flow capacity of different pipe sizes, and which is the best roof drain for a specific pipe size. Unfortunately, recommendations aren't that straightforward because you also need to account for water pressure, material friction and more.
You cannot directly convert PSI to GPM. They are two different units of measure. PSI measures pressure, and GPM measures flow rate. However, if other variables are known, you can use Bernoulli's equation to indirectly make a conversion. The following assumes the flow is in a pipe and the pipe diameter is known.