Note on sand filter size

According to which rule of thumb the sand filter was calculated.

It should not exceed a max filter speed of 50m/h.

Why 50 m/h?

This is a relatively high filter speed,which is considered the upper limit in some applications so that the sand filter is not overloaded and the filter medium works well.

The specified filter speeds are maximum values or upper limits at which the filter works efficiently and safely.

The rule of thumb of about 50 m/h (as in your table for larger filters) is a kind of "upper limit" for the filter speed.

For smaller filters (300–500 mm), slightly lower speeds (around 40 m/h) are often recommended to ensure filter quality and service life.

Summary: Yes, the values given in the table can be considered as maximum filter speeds. The actual operating filter speed can be chosen slightly lower depending on the application, water quality and filter manufacturer.