The Bosch External Water Filter (8703305356) replaces the internal water filter that comes with the heater. Having the water filter external means it is located under the Bosch Therm tankless water heater and is therefore easy to access and clean out. Odds are that if you do not install the external water filter then the internal water filter will not get regularly cleaned out as you would have to open the cover and remove the control board to get to the internal water filter, which is not very convenient. It is recommended to clean the filter screen at least once a year for periodic maintenance.
The Bosch Therm External Water Filter is designed to work with the following Bosch Therm Tankless Water Heaters: C 1210 ESC, GWH C 920 ESC, C 1210 ES, GWH C 920 ES, C 1050 ES, GWH C 800 ES, C 950 ES, 940ES, 940ESO, GWH 715 ES, and 830ES.
This accessory is not included with these heaters and is highly recommended.
The Bosch External Water Filter is included with the Bosch Integra 500 and Bosch Evolution 500 water heaters.
The Bosch External Water Filter is NOT compatible with the new Bosch Greentherm C950ES and Greentherm C1050ES tankless water heaters.
Replacement filter screens part 8700507059 are available for the Bosch External water filter. Please call us at 866-289-4652