The concepts of pressure loss and pump pressure are not always as clear as we think.
Glass filter media generates less pressure than silica sand inside the filter and this is the main reason for saving energy.
Pressure: It is the weight of the column of water existing per surface unit.
Manometers: (pressure measures) usually show you the pressure inside the filter in Kg/cm2.
If we have a one square centimetre column 10 meters high, this will weigh 1 kilogram. 1kg/cm2 = 10 meter water column.
As an example:
If we place a manometer on a pump, that must pump water up ten meters, it will show 1kg/cm2 (=10 meters water column). Now if we placed the manometer at the outlet at the bottom of a pool at two meters deep, it will show 0,2kg/cm2 (=2 meters water column)
It´s important to distinguish between inlet and outlet pressure .
The difference between the inlet and outlet pressure is the pressure loss given by the filtering material.
The average pressure loss is 0,6kg/cm2 using silica sand, and 0,05kg/cm2 using Glass Filter Media.
This small pressure loss difference between medias, is where the energy saving capacity lies.
THE ENERGY SAVING IN SWIMMING POOLS PUMPS IS DETERMINATED BY THE PRESSURE
The relation between the hight of the water column (pump pressure) with silica sand and glass filter media in swimming pools. Also known as glass filtering in pressure filters.
The pump manufacturer gives you a consumption curve, with a constant pressure. For example 0,5kg/cm2.
So if the pump performs within this range, it will consume the amount stated by the manufacturer. But if the pressure generated by the filter doubles the pump pressure, the electric consumption of the pump will be double also
A good example would be: A vehicle that consumes 7 liters every 100 kilometers. If you measure it for 100 kilometers downhill and then another 100kmts uphill. The consumption of the vehicle will vary depending on the power that is required to move it.
Meanwhile during downhill the consumption would be almost zero, during uphill the consumption will rise notoriously, even if the manufacturer indicates that the vehicle consumes 7 liters every 100 kilometers at a certain speed.