The filter medium is backwashed two to three times a year. The frequency of backwashing depends on nutrient input, water quality and bathing intensity. Most nutrients enter the water directly from the environment through wind pollution (e.g. pollen, Sahara dust or autumn leaves). But nutrients also remain in the water when swimming and splashing around. These nutrients are washed out of the filter by the backwash. In the first year of use of your Holc natural pool, our service team will carry out this backwashing for you as standard. In subsequent years, you can continue to enjoy our maintenance service as you wish - or you are welcome to carry out the backwashing yourself with the appropriate equipment.