The Bosch Protankless Lower O-ring, part number 87002050230, is a replacement sealing component designed for the lower seating position within the water valve assembly of compatible Bosch Protankless tankless gas water heaters. This O-ring maintains a watertight seal at the lower junction of the water valve, preventing water from leaking past the valve interface and preserving the pressure integrity of the heater's internal water circuit. It is a factory-specified replacement part used to restore proper sealing performance to the water valve assembly.
The lower O-ring occupies the lower seat of the water valve body and works in conjunction with the upper O-ring to fully seal the valve assembly against water passage. Extended service in a tankless water heater environment subjects O-rings to sustained thermal cycling, mineral deposits, and water pressure variation, each of which contributes to gradual compression set and seal degradation over time. Replacing a worn or failed lower O-ring restores the valve's sealing function and prevents water intrusion into adjacent internal components of the heater.
What's Included: One Bosch Protankless lower O-ring replacement seal, part number 87002050230.
Installation Limits: This O-ring is specific to the lower seating position within the water valve assembly and is not interchangeable with the upper O-ring used in the same assembly. Installation requires isolating the water supply, fully depressurizing the unit, and accessing the internal water valve by opening the heater casing before the O-ring can be removed and replaced.
Compatibility: Compatible with the Bosch Protankless 520HN tankless gas water heater water valve assembly.
