If a cistern has been properly built or installed, regular cleaning is not necessary. The sediment layer that forms on the bottom of the cistern serves to filter the water and should not be removed if possible, as it takes several months to form.
If a cistern still needs to be completely cleaned, you can do this yourself with the help of a dirty water pump and a high-pressure cleaner. The devices are available for daily rates from fifty euros in hardware stores or machine rentals. The purchase price for a high-pressure cleaner should be calculated from one hundred euros, while dirty water pumps are available from around 200 euros.
A professional cleaning company charges 200 to 300 euros for a pure internal cleaning of the water storage tank of a cistern. If filters, piping and, if necessary, an infiltration system are available, the costs can add up to 500 euros.