Abstract: A method of operating a horizontal filter well. Water is transported into a well from at least one roughly horizontally arranged train and distributed further from there. Pressurized water is forced through the horizontal filter train in the reverse flow direction, as a means to free the horizontal filter train of blockages. The pressurized water exits through the inlet orifices of the horizontal filter train and passes into the aquifer. A vertical well provided in the vicinity of the horizontal filter train suctions off the water exiting from the horizontal filter train, along with impurities removed from the horizontal filter train.