Bosch Washer Er:21 Reports Too Much Foam

What Er:21 means

Er:21 appears when the control senses a tub full of foam. Bosch's explanation is blunt: the detergent is wrong for the machine, or too much went in. The Vision manual's whole remedy is to talk with the owner about dosing. Suds get into the drain pump and confuse the pressure sensing, so the control spots the trouble and stops. Houston's hard water can also tempt owners to add extra soap.

Common causes of Er:21

Soap not designed for high-efficiency front-loaders
A heavy hand with detergent given the load and water hardness
Soap film left in the drum from many earlier loads

✓ One safe check you can try

1. Open the door and let the foam settle for half an hour. 2. Switch to a detergent marked HE or for front-loaders. 3. Use about half of what you would in a top-loader. 4. Run an empty rinse to flush the residue already in the drum. 5. Wipe the door seal and detergent drawer.

! Why to stop there

Pressing on with more cycles pushes suds into the pump and pressure tube, which can trigger other errors.
Dumping water or vinegar into the drum to cut the foam can add to the mess.
Putting more soap in to fix hard water usually makes the problem worse.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

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Er:21Er:21 questions

How much detergent is right?

Follow the line on the cap for your load size and soil level, and use less in soft water. Front-loaders need far less than top-loaders, and extra soap does not clean better.

Will this error come back?

Not if you cut the dose and use HE detergent. Residue already in the drum can cause one more round, so an empty rinse cycle helps clear it.

Can foam damage the washer?

Occasional suds will not, but heavy foam can leak out of the drawer and over-work the pump. Fixing the dosing is far cheaper than repairing a pump.