Water purification in multiple stages using mechanical and biological methods (sponge filters, activated carbon filters, bio-surface elements). Includes a water heater with externally adjustable thermostat. It has a separate, detachable pre-filter, offering convenience in terms of maintenance, reducing the frequency of filter cleaning. The pre-filter has a plunger for filling the filter with water during installation and after each cleaning. It also has two valves for flow control, one at the pre-filter point and one at the inlet/outlet of the filter, for adjustment and to prevent water leakage during the cleaning process.