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Bosch Dishwasher E12: Hard Water Scale
E12 is the code where your water, not a broken part, is usually the cause. Minerals have coated the pump assembly, and Bosch’s answer starts with descaling.
Bosch on E12
Bosch says an E12 error code indicates a build up of limescale in the heat pump. In Bosch parts listings, that heat pump is the circulation pump with a built-in heater, the part that moves and warms the wash water. Bosch’s article explains that dishwashers run so often that limescale can build up quickly, especially in hard water areas. Bosch recommends its own descaler to remove hard water deposits, and on models that come with a water softener it says to keep softening salt in the reservoir to prevent the scale from returning. Your owner’s manual shows whether your model has a softener and how to fill it. Source: Bosch E12 article (opens in a new tab).
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What Comes Before E12
Hard water leaves clues first.
Why Scale Builds Up
Bosch’s explanation, and what speeds it along.
Bosch’s E12 Advice
Follow your manual for the exact descaling program.
Descale
Bosch recommends its dishwasher descaler to remove hard water deposits and limescale.
Add softening salt
If your Bosch has a built-in water softener, fill the salt reservoir with dishwasher softening salt as the manual shows.
Know your water
Your city’s annual water quality report usually lists hardness, which helps when setting the softener.
When to Call a Technician
Schedule a repair if:
- E12 is back soon after descaling
- The water no longer heats
- E12 together with E09 or E21
- Scale is visible on the pump area
Bosch Hard Water Help
Bosch dishwasher repairMore help, including other Bosch codes:
Bosch dishwasher E24 error codeBosch dishwasher E25 error codeBosch dishwasher E15 error codeBosch refrigerator E02 error codeBosch oven E11 error codeAll Bosch appliance repairBosch E12 articleWritten estimate first
Scale Still a Problem?
We inspect the Bosch heat pump and heater for scale damage and give you a written price before replacing anything.
- Diagnostic fee credited toward the repair
- 90-day warranty, 6 months for members
- Open daily, 8 AM–8 PM
Bosch E12 FAQs
Bosch says E12 indicates a build up of limescale in the heat pump.
No. Bosch’s advice applies to dishwashers that come with a water softener. Your owner’s manual says whether yours has one.
Bosch’s article recommends its own descaler. Following the manufacturer’s product avoids guessing at what the seals and parts tolerate.
Scale is a water condition rather than a defect, so check Bosch’s warranty terms before assuming a claim. Our Bosch dishwasher repair page explains Bosch’s coverage.
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