Pumps				Filters
	Combined pump+ filter

Calculation of the pump characteristics

Basic rule : The pump has to circulate the contents of the swimming pool each 4 hrs.

The flow of the pump depends on the resistance which the water will encounter on it's way from the pump to the swimming pool. The resistance is being expressed in "meters water height "(1 bar = 10 m of water height).

A couple of "rules of thumb" can be used to estimate the resistance :
- Per 10 m distance between pump and swimming-pool inlet : 1 meter of water height
- Per 90 deg angle : 1 meter of water height
- Per meter that the pump is below the inlet of the swimming-pool inlet : 1 meter of water height
- Swimming pool solar heating unit : 1 meter of water height
- Filter : 1 meter of water height

Subsequently, one can read from the "pump curve" (x-axis = flow , y axis = meters of water height) the flow of the pump. In the example below, the total resistance = 8 meters of water height and the correspomding volume = 11 m3/h. This set-up is appropriate for a swimming pool of 44m3.

WanWhen do I need a sand filter ?

A paper filter can only remove coarse dirt. When you have problems with algae, it will be very difficult to remove it with a paper filter. In that case, one often has to dump the contents of the pool and start all over with fresh water. When the volume or the location of the swimming pool make a water dump undesirable, it is best to buy a sand filter.