Under normal circumstances, filtration takes place at a constant speed and fairly quickly.

You can check the flow rate of the Ultimate Star Filter® to see if your filtration time is correct.

In some cases, filtration may start, then stop or slow down considerably when there is still a lot of water in the top tank.

There are three main reasons for this

Lack of maintenance

Regular maintenance of your filters is necessary to remove any limescale or sediment deposits that may clog the outer pores of the filter. Read the maintenance instructions to find out how to clean your filters.

Faulty priming

When new filters are installed, or when they are cleaned or put back into service after a prolonged absence, they must be primed. Without this operation, your filters will not work properly. See our instructions on priming filters.

End of filter life

The closer you get to the end of the filter's life, the more the flow rate will tend to decrease, due to saturation of the filter and its clogging by limescale or natural sediments in the water.

The fact that some residual water remains in the upper tank after filtration is complete is not the same problem - it's a normal phenomenon.