-> being equal, it seems that any amount of pumping action would move
-> the water no matter how high you are above the equal static levels.
 
EH>Sorry Russ, but even if you provide a perfect vacuum you can only
EH>lift water a certain distance.  You see, it's not the vacuum that
EH>raises the water but the pressure on the surface.  Since you only
EH>have about 14 PSIG (One atmosphere) of pressure ON the water to
EH>force it up the pipe, there's a practical limit to how far that
EH>can be. It's even stranger when you're trying to pump water over a
EH>hill. It only takes about thirty foot of hill and you're SOL!
 
RS> I understand this IF you're pulling the water up a pipe. One
RS>atmosphere can push only so many ounces of water only so far.
 
RS> But, if you're PUSHING the water up, you can supply MUCH more
RS>force than one atmosphere. Just ask someone on the top floor of a
RS>skyscraper. 
 
You are certainly correct, Robert: There is no theoretical limit to 
pumping vertically when pushing.  I'm sure Elvis was referring only to
pumping by suction lift. When lifting by suction, the practical limit 
is usually taken as 28 feet, due to friction losses in the pipe and 
pump inefficiencies. Also, water under low pressure may "boil" , 
separating in the pipe and causing the pump to "loose traction" on 
the fluid.  This can occur microscopicly as well.  A source of damage 
to pump impellers is the formation and collapse of vapor cavities on 
the impeller, causing cavitation pitting.
 
When pushing, the sky is the limit.  We have some single stage
centrifugal pumps where I work that push their discharge up several 
hundred feet. Positive displacement pumps can produce enormous 
pressures, witness hydraulic systems, and I have read of special pumps 
capable of 60,000 psi. That pressure would allow a vertical rise  
of 26 MILES.
 
Pumping is often done in stages, as another contributor to this 
thread noted, but that is not due to theoretical considerations as he
seemed to be erroneously suggesting, unless for some reason the pumping 
task is restricted to a pump capable of only suction lift.  Most pumps 
both pull and push. Pumping in stages would be done for practical and 
economic reasons, and then usually in stages much greater than 33 feet.  
For example, one might pump in stages of 450 feet vertical rise if it 
was desired to use 200 psi rated pipe at the lower end.
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