I need to calculate the head capacity required at the pump, to pump sea water from a depth of 100m below sea level i.e. inlet is at 100m below sea level, the recieving end is at 5m above sea level. The flow rate shall be 100 litres/second. Length of the pipeline is 500m, inner diameter of the pipe is 800mm.

I believe that the potential head that the pump is just 5m and not 100m+5m, because water rises up to mean sea level without any effort from the pump. Is my thought correct, or should water be pumped with certain potential head to attain the required flow rate and how is it calculated?

Total head will be potential head + head loss due to friction + head due to desired delivery pressure at outlet

  • $\begingroup$ Where is the pump? $\endgroup$
    – Solar Mike
    Apr 8 at 14:30
  • $\begingroup$ water rises up to mean sea level without any effort from the pump ... that is not quite true ... temperature and salinity affect the density of the water $\endgroup$
    – jsotola
    Apr 8 at 16:18
  • $\begingroup$ @Solar Mike : the pump is at 5m above sea level at the outlet end. $\endgroup$ Apr 8 at 18:12
  • $\begingroup$ @jsotola: can you explain more, does it mean that the pump must suck water up. The pump is at the outlet end which is at 5m above sea level. $\endgroup$ Apr 8 at 18:14
  • $\begingroup$ if the water at the 100 m depth is more dense than the surface water, then yes ... you also have to take the friction of the pipe into account $\endgroup$
    – jsotola
    Apr 8 at 18:45


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