Pump Intake Flow Run
This is a competitor's pump station showing a correct flow run into the pump intake. This straight run of pipe provides smooth laminar flow into the impeller eye.
This is an Irrigation Craft flow run into the pump intake. Notice that the pump has flanged connections instead of threaded, and the intake flow run is manufactured by welding a straight piece of schedule 40 steel pipe into a weld flange and then hot dip galvanizing the assembly. The result is maximum thickness, low turbulence, maximum corrosion protection, and therefore a long service life.
How Not to Connect to a Pump Intake Connection
Below are photographs of manufactured pump stations with commonly seen errors on the pump intake connections. These errors have unpredictable outcomes and no one knows when a serious problem will occur.
When a problem does occur the owner may still never know what the cause is, all the owner may know is "they sure don't make pumps like they used to".
Example 1
The pump intake connection is directly to a 90 degree ell. This sharp turn in the water flow causes turbulence and uneven flow into the eye of the impeller. The intensity of the problems caused by this are variable, but ells can cause an unbalanced loading of the impeller leading to vibration problems. This pump station was reported by the owners to have lost the impeller and motor numerous times in the 3 years the owners operated the pump station before they totally replaced it. Was the problem due to the ell?
Example 2
The pump intake connection is directly to a check valve on a manufactured pump station. Once again, this can cause turbulence and uneven flow into the eye of the impeller. Results are unpredictable.
The following information is shown with permission of Steve Harrington at Flometrics. This group of engineers are devoted to their craft. Please visit their site:
This still photograph and the movie illustrate Suction Turbulence resulting in reduced pump performance. The photograph and the video were made to analyze poor pump performance. Notice that the intake feed pipe expands just as it reaches the pump (rather than a straight pipe run). The turbulent eddies are clearly visible on the right. These eddies prevent an even smooth flow of water into the eye of the impeller (at bottom). The impeller would then become unevenly loaded and vibration would result as well as loss of efficiency, and possibly cavitation may occur due to the high velocity turbulence.
It would be difficult and expensive to accurately determine the effect of not providing a correct flow run into the pump on a specific installation. Therefore a "standard industry practice" is adopted by many to avoid the situation shown in the movie. Violate the standard practice enough times and eventually you will experience the problem.
