Do I need to change the water regularly?

With an outdoor pool, you don't have to change the water at all, because it renews itself completely within 1.5 years purely through rainwater: A 4x8 meter pool holds 37,500 liters of water, and with an average annual rainfall in Germany, 25,000 liters of rainwater are added to the pool per year. In 1.5 years, the pool's content is completely renewed. With an indoor pool, this is naturally somewhat different: Here, fresh water must be continuously added, if only to compensate for evaporation. The water should be changed completely once every three to five years, because the chloride levels in the water also rise over time.