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Bosch 125HX Water Heater Parts Diagram and Service Guide
Comprehensive parts identification guide for the Bosch 125HX water heater, featuring an exploded view diagram and a complete list of replacement components with part numbers.
Table of contents
Quick guide from the manual
This document serves as an official reference for identifying internal components of the Bosch 125HX water heater. It provides an exploded view diagram and a corresponding parts list to assist in maintenance and repair. Please note that part numbers may have changed over time; verify the specific part number against your unit's requirements before ordering.
Interior components diagram
The diagram illustrates the assembly of the 125HX unit, showing the relative positioning of the heat exchanger, gas valves, water controls, and ignition system. Use this visual guide to locate specific components during inspection or repair.
Parts list and identification
The following list details the key components identified in the diagram. Note that some parts are specific to the fuel type (NG - Natural Gas or LPG - Liquefied Petroleum Gas).
- Burner System: Main burner (7), Pilot burner (10), Pilot injector (12), and Set of electrodes (11).
- Gas Control: Gas valve (15), Pilot electrovalve (17), and Burner electrovalve (18).
- Water System: Hydro-generator (20), Water valve (24), Diaphragm (26), Water strainer (27), and Volumetric water governor (29).
- Safety and Ignition: Ignition unit (31), Flue gas safety device (34), and Temperature limit sensors (6, 23).
- Structural and Plumbing: Front cover (1), Draught diverter (4), Heat exchanger (5), and various pipes and gaskets (19, 21, 22, 39, 40).
Maintenance and repair notes
When performing repairs, ensure the unit is disconnected from gas and water supplies. The diagram highlights critical O-rings (37, 38) and gaskets (39) that should be inspected for wear during any disassembly. If a specific part is not found in this document, consult the official Bosch parts portal for the most current catalog information.
Manufacturer information
Bosch
Practical help
Common problems
Part identification mismatch
Bosch has updated part numbers over the years. Always verify the part number against the specific serial number of your unit.
Fuel type confusion
Ensure you select the correct part for your gas type (NG or LPG), particularly for burners, injectors, and gas valves.
Before use
- Verify the model number is 125HX.
- Identify the fuel type (NG or LPG) used by the appliance.
- Consult the exploded diagram to locate the faulty component.
- Cross-reference the item number from the diagram with the parts list table.
- Check for specific gas-type variants (NG/LPG) listed in the table for the required part.
Specs in practice
- Hydro-generator (20)
- Component responsible for generating ignition power from water flow.
Model compatibility
- Parts are specific to the 125HX model.
- Some components are not interchangeable between Natural Gas and LPG versions.
Manual page author
David Miller
Documentation analyst
Organizes user manual content into clear summaries, with attention to model details, product context, and everyday usability.