Meiko Commercial Dishwasher Error Code 426: Osmosis Membrane Dirty
Message 426 on a Meiko M-iClean U with reverse osmosis means the osmosis membrane is blocked or dirty. The maker says it is possible to continue, to check the pre-filter and replace it, and to call a service technician. Plan a visit for the membrane.
Low: the maker says operation can continue, but the membrane needs service.
- Code
- 426
- Maker
- MEIKO
- Equipment
- Dish machines
- Applies to
- M-iClean U (red/gray messages)
What does MEIKO error code 426 mean?
The osmosis membrane is the part of the reverse osmosis system that actually cleans the rinse water. Scale and sediment slowly build up on it, and as that happens it passes less water. When the M-iClean U control decides the membrane is blocked or dirty, it shows message 426. The manual allows operation to continue, which makes it a service warning, not a stop. The maker's steps are to check the pre-filter and replace it, since a worn pre-filter lets more sediment through, and to call a service technician for the membrane. A dirty membrane makes less treated water, so staff may see lower rinse water output over time and, eventually, the holding tank messages. Water hardness is a big factor: hard supply water loads a membrane faster, and the time since the last service also counts. The longer it stays dirty, the harder it is to restore, so it is better to schedule the work while the machine is still running normally.
Affected models and control systems
This is for Meiko M-iClean U undercounter dishwashers with a reverse osmosis system. Other ranges and machines without reverse osmosis use other messages.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- Message 426 on the display
- Treated water tank taking longer to refill
- Rinse water output falling over several weeks
Possible causes
Listed in MEIKO's documentation
- Pre-filter used up or clogged
- Membrane fouled by scale or sediment
- Water hardness
- Time since the last service
Other likely causes — what usually sits behind error code 426 on this control. A technician confirms which one it is before any part is replaced.
- Pre-filter changes that were skipped, so sediment loaded the membrane
- Mineral scale from hard supply water that built up on the membrane surface
Safe checks before calling for service
- Check the pre-filter and replace it, as the maker says.
- Keep working. The machine can continue for now.
- Watch for the tank messages 421 to 423 and note when they appear.
- Plan a service visit for the membrane.
- Call us to schedule it, and tell us the date of the last filter change.
How a technician diagnoses error code 426
- Confirm 426 and check the history of the pre-filter changes.
- Measure inlet pressure and water hardness.
- Compare module output and rejection with expected values.
- Inspect the membrane for scale or fouling.
- Clean or replace the membrane as the test shows.
- Record the result and set the next service date.
- Removing the membrane needs the system shut down and depressurized, with a risk of water on the electrics.
- Judging whether a membrane can be cleaned or must be replaced needs output and quality readings.
- Using the wrong cleaning product on a membrane can ruin it.
How error code 426 differs from similar codes
Message 408 is the pre-filter change prompt, and 426 is about the membrane behind it.
Technical reference
- Document
- M-iClean U Original operating instructions 9763258 (update 2026-06), 9.4.1 Messages p.43-45
- Edition
- 9763258 / Valid from: 2018-09 / Update: 2026-06
- Models / control
- M-iClean U (red/gray messages)
- Section
- 9.4.1 Messages, printed pp. 43-45 of 70 (PDF pp. 43-45)
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related MEIKO dish machine error codes
Can I keep running the machine with 426?
Yes, the maker says it is possible to continue. Plan the service though.
Will changing the pre-filter clear 426?
Not necessarily. A fresh filter protects the membrane but may not clean one that is already fouled.
How soon should I call?
Soon, because a membrane left dirty gets worse.
Need help with MEIKO error code 426?
A technician confirms the cause on site and gives you the price in writing before any work starts.