I am trying to figure out how high my pump will suck water from a pond. I have a twelve inch suction line going into the pond. My pump sits on the berm that is 18 feet Higher than the end of the suction line. I need to know if my pump will suck water that high. Is there a way to calculate this? Any help is greatly appreciated.
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Help pumping from a pond?
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Yes,
You need to calculate the net positive suction head which varies from about 34 feet at sea level to less than 20 feet in Denver, CO which is at about 5000 feet above sea level. Any good pump handbook will show you how to calculate this of try the Hydraulic Institute Engineering Data Book or King's Handbook of Hydraulics. You'll need to know the pumping rate too.
You need to calculate the net positive suction head which varies from about 34 feet at sea level to less than 20 feet in Denver, CO which is at about 5000 feet above sea level. Any good pump handbook will show you how to calculate this of try the Hydraulic Institute Engineering Data Book or King's Handbook of Hydraulics. You'll need to know the pumping rate too.
A few of comments -
1) The total static head is the difference in the pond water level and the height to which you pump the water. The length of the piping is used to determine the dymanic head or friction head, which is a function of flow rate, pipe diameter, pipe roughness and fittings.
2) You will propably need to prime the pump in order to get any water out of it.
3) The absolute maximum Net Positive Suction Head is the difference between the atmospheric pressure and the pressure that water will boil at your temperature. The pump's suction will cease to be effective if it vaporizes the water. You will also damage the impellor. A pump can push water much higher than water can be pulled. Clifford H Laubstein
FL Certified PE #58662
1) The total static head is the difference in the pond water level and the height to which you pump the water. The length of the piping is used to determine the dymanic head or friction head, which is a function of flow rate, pipe diameter, pipe roughness and fittings.
2) You will propably need to prime the pump in order to get any water out of it.
3) The absolute maximum Net Positive Suction Head is the difference between the atmospheric pressure and the pressure that water will boil at your temperature. The pump's suction will cease to be effective if it vaporizes the water. You will also damage the impellor. A pump can push water much higher than water can be pulled. Clifford H Laubstein
FL Certified PE #58662
Or, easier still, mount the pump on a floatable platform in the pond. This will reduce the suction head from 18 feet to probably a foot or two. If this is possible.
You can't "pull" water. It is the atomspheric pressure which pushes water into the pump.
You can't "pull" water. It is the atomspheric pressure which pushes water into the pump.
Like the others have said before, you will need to find a good book on pumps and piping systems design. Most pump manufacturer's will help you with this if you provide them your NPSHA for the proposed system.
NPSHA = Atmospheric pressure(converted to head) + static head + pressure head - the vapor pressure of the liquid - the friction losses in the piping, valves and fittings
The NPSHR is provided by the mnfr for each pump. To stop the liquid from vaporizing at the low pressure side of the pump; net positive suction head available (NPSHA) must be equal to or greater than the net positive suction head required (NPSHR)).
Some easy things to eliminate cavitation, of which some have been mentioned before:
-Lower the pump to the source and reduce the height of 'suction'
-Reduce the friction on the suction side by reducing fittings or using lower friction pipe
Or if you haven't finalized the system, cosider 'pushing' the water. I worked on an irrigation pump station a few years ago, where I installed a well pump inside wetwell adjacent to a lake. This eliminated the NPSH problems and provided me with more flow with less power consumption (as opposed to the sigle stage options available to me at the time).
The pump priming point that was brought up by gibfrog is very important also. You may be able to just meet your NPSH requirement but if your suction line drains during pumping cycles you will have to reprime the pump. A check valve at the inlet will help, but creates friction that will reduce your NPSHA.
NPSHA = Atmospheric pressure(converted to head) + static head + pressure head - the vapor pressure of the liquid - the friction losses in the piping, valves and fittings
The NPSHR is provided by the mnfr for each pump. To stop the liquid from vaporizing at the low pressure side of the pump; net positive suction head available (NPSHA) must be equal to or greater than the net positive suction head required (NPSHR)).
Some easy things to eliminate cavitation, of which some have been mentioned before:
-Lower the pump to the source and reduce the height of 'suction'
-Reduce the friction on the suction side by reducing fittings or using lower friction pipe
Or if you haven't finalized the system, cosider 'pushing' the water. I worked on an irrigation pump station a few years ago, where I installed a well pump inside wetwell adjacent to a lake. This eliminated the NPSH problems and provided me with more flow with less power consumption (as opposed to the sigle stage options available to me at the time).
The pump priming point that was brought up by gibfrog is very important also. You may be able to just meet your NPSH requirement but if your suction line drains during pumping cycles you will have to reprime the pump. A check valve at the inlet will help, but creates friction that will reduce your NPSHA.
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