- Appliances
- Water softeners
Err 1
BWT Err 1 on water softener: valve controller error
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
High
Quick answer
The “Err 1” message with an audible alarm on a BWT water softener means the controller failed to detect the valve home position within 10 minutes. Check that all power leads are secure and switch power off for 15 seconds until PF shows to reset.
Safety first
Stop and check this first
- Plug the transformer into the wall socket with the socket switch in the OFF position, and never open the electronic control head yourself.
- Always isolate the water softener from the mains electricity supply before any maintenance or repair work, and use only the plug-in transformer supplied with the unit.
Safe checks you can perform
- Check that the plug-in transformer and leads are secure
- Turn power off for 15 seconds until PF shows, then turn back on
- Place the softener on bypass if Err 1 persists or drain runs constantly
Leave these tasks to a qualified professional
- Do not attempt this professional task: Control valve home-position and controller diagnostic
- Do not attempt this professional task: Replacement of faulty control or wearing parts by qualified staff
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Control valve home-position and controller diagnostic
What they doAn authorised BWT service technician inspects the control head, servo motor and position detection to find why the home position was not reached within 10 minutes.
They must show youthe control valve completing its positioning cycle into the service position without triggering Err 1.
In writingthe softener model and serial number, the fault found in the positioning cycle and the test result.
Replacement of faulty control or wearing parts by qualified staff
What they doIf the technician identifies a defective controller, drive assembly or wearing part, they replace it with genuine BWT parts and verify settings and leak-free operation.
They must show youthe replaced part and the display back in normal operation with the capacity bar visible.
In writingthe parts replaced, the programmed water hardness and time, and the service warranty terms.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Check that the plug-in transformer and leads are secure
- Who:
- you, without opening the control head or internal covers.
- How:
- inspect the fused switched wall socket and the low-voltage lead from the plug-in transformer (or battery pack where fitted) at the terminal on the rear of the softener, making sure every connection is firmly seated.
- Result that matters:
- a secure power connection before you reset the controller.
- If a plug or terminal was loose:
- seat it firmly and proceed to the 15-second power reset.
- If all external connections are already tight:
- move straight to the power-off reset.
- Evidence to keep:
- a photo of the Err 1 screen and of the transformer and rear power terminal.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
Turn power off for 15 seconds until PF shows, then turn back on
- Who:
- you, at the softener's switched power socket.
- How:
- switch the power off for 15 seconds on a BWT Perla Silk (or 10 seconds on a BWT WS model) until PF (power fail) is handled on the display, then switch it back on and allow up to 5 minutes for the valve to move into the service position.
- Result that matters:
- the valve movement stopping in the service position with Err 1 cleared from the display.
- If Err 1 clears and the unit returns to service:
- check and reset the present time on the display if needed.
- If Err 1 and the audible alarm return after 10 minutes:
- stop repeating power resets.
- Evidence to keep:
- a short video of the valve positioning sound and whether PF appeared during the reset.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
Place the softener on bypass if Err 1 persists or drain runs constantly
- Who:
- you, using the external inlet, outlet and bypass valves.
- How:
- if Err 1 comes back or water runs constantly to the drain outside recharge mode, open the bypass valve (D) and close the inlet valve (C) and outlet valve (E) as shown in BWT's installation layout.
- Result that matters:
- uninterrupted household water supply while the softener is isolated for service.
- If the unit is isolated on bypass:
- contact your BWT stockist or after-sales service team.
- If you also notice water in the brine cabinet reaching the overflow:
- note this for the engineer.
- Evidence to keep:
- the valve positions set and the time you isolated the unit.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Appliances
- Brand
- BWT
- Product type
- Water softeners
Known code variants
- BWT Err 1
- BWT Err1
- BWT Perla Silk Err 1
- BWT softener Err 1 controller error
- BWT WS Err 1
- Err 1
- Err1
- error Err 1 BWT
- fallo controlador BWT Err 1
What it means
In the BWT Perla Silk (S, M, L and XL) and BWT WS Range (WS155 to WS755) installation and operating manuals, the main display shows “Err 1” and sounds an audible alarm when the home position is not detected within 10 minutes, indicating a controller error. BWT notes that this error condition can only be cleared by removing and re-applying electrical power. Other BWT models may differ, and the code alone does not prove that the control head, servo motor or PCB is defective.
Warnings and stop conditions
- Mediumeditorial warning
Plug the transformer into the wall socket with the socket switch in the OFF position, and never open the electronic control head yourself.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual
- Highsource verified
Always isolate the water softener from the mains electricity supply before any maintenance or repair work, and use only the plug-in transformer supplied with the unit.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
Symptoms and causes
Probable causes · in order
- Home position not detected within 10 minutesCommon
BWT states that if the motorised control valve does not find its home position within 10 minutes, the main display triggers Err 1 and sounds an alarm.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
- Loose power connection or power interruptionCommon
BWT's first troubleshooting step for Err 1 is to verify that all connections are secure and cycle the power supply so the controller can reset.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
- Persistent controller or valve drive faultPossible
When Err 1 remains after checking the leads and resetting the power, BWT instructs you to call your local dealer or after-sales service team.
Evidence: BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual · BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
Virtual technician
Does Err 1 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
BWT Perla silk S, M, L, XL Duplex softening unit - Installation and operating manual
BWT · 2019 · official_doc
- 2
BWT WS Range Water Softener (WS155-WS755) - Fitting and operating instructions
BWT · 2025 · official_doc
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