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John Guest push in fittings & Polyethylene Tubing
Water Flow Chart #1 The chart below takes into consideration the potential damage from hydraulic hammer (shock) and noise considerations due
to excessive fluid velocity. You can flow more than what is shown in the chart (see Chart #2 below) however, you may run into problems if you do.
Water Flow Chart #2
Water Flow Chart #3
There are now 3 charts and one formula on this page showing water flow through a pipe. These 3 charts come from 3 different sources, and they all are just general guidelines. and should not be relied on as a precise source for information or as a substitute for engineering. The data between them does vary. In the chart to the left is a general guideline for how much liquid a pipe of specific size can flow in GPM (Gallons Per Minute) & GPH (Gallons Per Hour.) There are three columns. (Well there are really six, but each colum is shown in Gallons per minute, and then again as Gallons per Hour.) The first set of columns would be the minium you would expect for the pipe size shown using nothing but gravity in a low head pressure situation to power the flow. The 2nd set of columns show what you can expect using an average pump with a pressure from 20 to 100psi. The 3rd set of columns is the maximum flow based on maximum recommended velocity of the liquid in the pipe. You may exceed this, but you will have to contend with excessive noise and exceedingly high inertial impacts. (I.e. Possible system failure due to hydraulic hammer effects.) This is a very general guide and is subject to many variables. Pressure, noise allowance, bends, fittings, viscosity, etc. affect how much liquid will flow through a pipe of given size. If you can accept more noise and have higher pressure, you can pump more at the risk of system failure. If you have a lot of bends and fittings you will flow less. The flow rates shown should not produce unacceptable noise, however, many variables affect noise, so this is no guarantee that the system will be noiseless. Sometimes experimentation is the only sure way to know if a system will be noisy or not. The flow rates shown are for water, with viscosity of 1. Higher viscosity liquids will flow less, lower viscosity liquids may flow more. You can use the Hazen-Williams equation below to calculate the exact flow loss through a pipe.
If you really want to get technical and calculate the exact friction loss through PVC and CPVC pipe you can use the Hazen-Williams equation as expressed below for water:
f = 0.2083 (100/c)1.852 q1.852 / dh4.8655
f = friction head loss in feet of water per 100 feet of pipe (fth20/100 ft pipe)
q = volume flow (gal/min)
dh = inside diameter (inches)
c = a constant for internal pipe roughness. 150 is the commonly accepted value for PVC and CPVC pipe.
You can also print out and use the Nomograph courtesy of Plastics Pipe Institute, a division of The Society of
The Plastics Industry. (Note: You normally want to keep your flow velocity under 12 feet per second for 4" and under and 5 feet/second for 5" and above to avoid hydraulic shock.)
What about fittings? How do they effect flow? See our Friction loss due to pvc pipe fittings chart.
Compared to other materials on construction for pipe, thermo-plastic pipe smoothness remains relatively constant throughout its service life.
If you are flowing something other than water, you'll have to adjust the formula for the viscosity of the liquid you are flowing.
Note: One of the benefits of using Flex PVC pipe is being able to make long gradual bends instead of using fittings which will allow more flow with less noise, less back pressure, and less load on the pump. In other words, a more efficient system.