Water in the AdBlue tank
Water in the AdBlue tank dilutes the urea below the 32.5% that ISO 22241 specifies, so the system under-doses, NOx conversion fails and a fault follows. It is usually recoverable by drain and flush — call 01295 380724.
AdBlue is 32.5% urea in demineralised water for a reason: that is the eutectic concentration, the one that freezes lowest and doses predictably. Dilute it and you have not made a weaker but working fluid — you have made a fluid the dosing map is wrong for. The engine management doses on the assumption of 32.5%, under-delivers ammonia, fails its NOx conversion check and logs a fault. Tap water adds minerals on top; demineralised does not, but the concentration problem remains.
Call 01295 380724 From just £89 call-out fee
Water in the AdBlue tank — the severity verdict
| Severity | Likely recoverable Usually resolved by a drain and flush, with a fluid-quality check afterwards. |
|---|---|
| What went where | Water in the AdBlue tank |
| Direction | Into the AdBlue tank |
| Typical cost | £170–£360 typical total, from a £89 call-out |
| Time on site | About 60 minutes |
| Call-out | From just £89 call-out fee |
| Helpline | 01295 380724, 24 hours |
£89 is the call-out. An AdBlue tank drain and flush is quoted on the phone before a technician travels. If the SCR system needs component replacement — dosing injector, pump, tank or catalyst — that is separate, and you will be told before any work starts. If this is a job we cannot fix at the roadside, we will tell you that on the phone rather than after we arrive.
What to do right now
- Note whether it was tap water or demineralised — it changes the flush.
- Avoid unnecessary running.
- Do not attempt to correct the concentration by adding AdBlue.
- Call 01295 380724.
What a technician actually does
Drain, flush, refill with fresh AUS 32, read and clear the stored NOx and dosing codes, and a short dosing verification.
Why this is not the same job as the other direction
This is contamination of the SCR dosing circuit — tank, metering pump, heated lines, dosing injector and potentially the catalyst. It is not the fuel system, and it is not the cheaper job. Anyone quoting a flat drain price for this has not looked at the system.
Common questions
Surely AdBlue is mostly water anyway?
It is 67.5% demineralised water — at one specific concentration. The dosing strategy is calibrated to that concentration. Dilution is not a milder version of the same fluid.
Can I top it back up with concentrated urea?
No, and concentrated urea is not what is sold to you. The fix is to remove the wrong fluid, not to chase a ratio.
Will it damage anything?
Dilution alone usually does not damage components. The cost is the drain, the flush and the fault clearing — plus any miles driven with NOx conversion out of spec.
What customers say
4.8 out of 5 from 2,190 Trustpilot reviews. What reviewers mention most is that the technician stayed calm and professional with a driver who was embarrassed and stressed, and that somebody arrived when they said they would.
The most common criticism is price. People do not expect a wrong-fluid job to cost what it costs, and that is a fair complaint to publish rather than bury. The answer is the From just £89 call-out fee, a quote given on the phone before a technician travels, and being told when a job cannot be done at the roadside rather than after somebody has arrived and charged for the visit.
Related AdBlue problems
Start from a symptom instead
Where we cover
Who you are dealing with
AdBlue in Fuel is a service by Forecourt Assist. Forecourt Assist is a trading name of Fuel Fixer Ltd, company no 08520551, registered at Fairway House, Portland Road, East Grinstead, RH19 4ET, a company of Fuel Fixer International. Fuel Fixer International is owned by Stockbridge Capital Holdings.
Reference: Urea (Wikipedia).
Across the Fuel Fixer network
These are sister brands of the same company, not unrelated sites. Forecourt Assist keeps the canonical list at forecourtassist.co.uk/network rather than duplicating it here.