How much water flow at low speed?

[mas985]

That is correct and prettyr typical of two speed pumps. The energy consumption is usually about 1/3 of high speed but you have to run twice as long so the effective energy consumption is 2/3 or about 1/3 savings. Different pumps will vary slight about this number but they are all pretty close.

By the way, if you look at any two speed pump head curve, you can actually prove the pump affinity equations. The example you gave has 1/2 the GPM at 1/4 the head which is exactly what the affinity equations predict. The entire low speed curve is simply a scaled version of the high speed curve.