fafrd said:Isn't 'head' the difference in height between incoming liquid and outgoing liquid? if you raise the pump all the way to the level of the liquid in the keggle, I don't think the 'head' has changed (and I suspect the flow rate will not change either).
Half a keggle is about 12", so if my understanding is correct, your (very helpful) test only demonstrated the flow rate at about 12" of head (not 40").
I checked quickly for a definition and could not find one, so I could be wrong on this understanding of 'head', but I am pretty sure that the correct test for 40" of head would be to pump from one keggle on the floor to a second keggle on a table with 40" of height between the liquid levels of the two keggles (and the position of the pump should not really matter as long as it is somewhere between the lower keggle valve and the liquid level of the upper keggle).
-fafrd
Oooohhhh, I always thought it was from the pump location.