What does filter-bed expansion mean in practice?
During reverse flow, the layer increases in height, and the degree of expansion depends on the grain density, temperature and water velocity.
When does it matter?
Too small expansion does not remove the sediment, and too large expansion flushes the medium into the sewage system.
Which solutions are related to it?
The drain restrictor and free space are selected and the actual lift is checked at the coldest water.