×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Help pumping from a pond?

Help pumping from a pond?

Help pumping from a pond?

(OP)
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.

RE: Help pumping from a pond?

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.

RE: Help pumping from a pond?

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

RE: Help pumping from a pond?

Call the manufacturer of your pump and get the specs from them. If you ask, they will also answer your questions.

RE: Help pumping from a pond?

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.

RE: Help pumping from a pond?

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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources