The circulation system of the pool

It is important that the pools circulation system works as it should, in order for you to be able to enjoy your pool and have many pleasant moments of bathing.


Water leaves the pool via a skimmer, equipped with a flap, which adjusts to the water surface. This makes the flow rate at the surface increase and suck particles on the water surface into the skimmer.

The particles are collected in a filter basket, which must be emptied regularly, about once a week. If your pool has a main drain the flow must be controlled so that about 30% of the water is taken from the bottom and about 70% from the skimmer.


The water returns to the pool cleaned and heated via the inlets. These should be directed slightly upwards to facilitate cleaning of the surface water.


Pool pumps create suction in the skimmer and then push the water through the pool filter, through the pool heater and then back into the pool via the pool inlets. The pumps pre-filter strainer basket must be emptied regularly, e.g. during backwashing.

Before start, make sure that the pump is filled with water to avoid damage to the pumps shaft seal. If the pump is located above the pool surface, water flows back to the pool when the pump´s is stopped. When the pump then starts, it may take a while before the pump evacuates all the air in the suction pipe and start pumping water.

This can be remedied by closing the valve before closing the pump and then immediately turning off the pump. This retains the water in the suction pipe.


The pool’s mechanical cleaning takes place via the pool filter, which filters out particles down to about 25 µm (thousandths of a millimetre). The central valve on the filter tank controls the water flow through the filter.

The filter is 2/3 filled with filter sand, grain size 0.6-0.8 mm. As the dirt accumulates in the filter, the backpressure increases and is read off in the central valve’s pressure gauge. The sand filter is backwashed once pressure increases by about 0.2 bars after the previous backwashing. This means reversing the flow through the filter so that the dirt is lifted from the sand and flushed down the drain.

The filter sand should be replaced after 6-8 years.


After the filter, a heater that heats the pool water to a pleasant temperature is placed. An electric heater, heat exchanger connected to the building’s boiler, solar panels or heat pumps, can heat the water. Adjust the thermostat to the desired pool temperature.