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Bosch 125B Water Heater Interior Components and Parts Guide
A comprehensive parts identification guide for the Bosch 125B water heater, featuring an exploded view diagram and a complete list of internal components with corresponding part numbers.
Table of contents
Quick guide from the manual
This document serves as a technical reference for identifying internal components of the Bosch 125B water heater. It includes an exploded view diagram and a corresponding parts list. Please note that while these parts are primarily for models built after February 2003, many are compatible with older units built before January 2003. Always verify part numbers before ordering, as Bosch may update them over time.
Interior Components Diagram
The diagram provides a visual representation of the internal assembly, including the heat exchanger, main burner, gas valve, water valve, and various sensors. Each component is numbered to correspond with the official parts list.
Parts List
The following list identifies key components and their associated Bosch part numbers:
- 1: Cover (8 705 421 025)
- 2: Temperature adjustment knob (8 702 000 111)
- 5: Heat exchanger (8 705 406 235)
- 9: Main burner (8 708 120 298 NG / 8 708 120 296 LP)
- 10: Pilot burner (8 718 105 051)
- 17: Gas valve (8 707 021 090 NG / 8 707 021 091 LP)
- 20: Thermocouple / Flue Gas Sensor (8 707 206 074)
- 21: Water valve (8 707 002 649)
- 24: Diaphragm (8 700 503 053)
- 25: Water inlet filter (8 700 507 001)
- 31: Overheat sensor (ECO) (8 707 206 040)
Manufacturer information
Bosch
Practical help
Common problems
Part number mismatch
Bosch frequently updates part numbers. Always verify the specific part number against the current manufacturer database before purchasing.
Model year compatibility
While the diagram is for models built after February 2003, many parts are backward compatible with units built before January 2003.
Before use
- Identify the specific component needing replacement using the exploded diagram.
- Verify if your unit requires Natural Gas (NG) or Liquid Propane (LP) parts, as some components like the main burner and gas valve differ.
- Check the manufacturing date of your unit to ensure part compatibility.
- Cross-reference the part number from the list with the latest manufacturer data.
Images and diagrams
- The diagram shows the physical layout of the internal components.
- Numbers in the diagram correspond directly to the items in the parts list.
Model compatibility
- Parts are primarily for Bosch 125B models built after February 2003.
- Some parts are compatible with older 125 series models built before January 2003.
Manual page author
Michael Turner
Technical manual editor
Reviews PDF manuals for structure, safety notes, and practical product details so readers can find the right information quickly.