Yes — diesel exhaust fluid (DEF), also known as AdBlue®, does require special storage. While DEF is non-hazardous, it is highly sensitive to temperature, contamination, and incorrect handling. If it isn’t stored correctly, it can degrade, crystallise, or become contaminated, leading to equipment downtime, costly repairs, and non-compliance with emissions regulations.
Understanding how to store DEF properly helps protect both your machinery and your investment.
What is Diesel Exhaust Fluid (DEF)?
Diesel exhaust fluid is a high-purity solution made from 32.5% urea and 67.5% deionised water. It is used in vehicles and equipment fitted with Selective Catalytic Reduction (SCR) systems to reduce harmful nitrogen oxide (NOx) emissions.
If DEF quality drops or the fluid is unavailable, SCR-equipped machines can lose power or shut down entirely. This makes correct storage just as important as having enough DEF on site.
If you’re looking for a deeper overview, have a read of our full guide on what AdBlue is and why proper AdBlue storage is so important.
Why DEF requires special storage
Unlike diesel, DEF is extremely sensitive to external conditions. The main risks are:
- Contamination from dust, fuel, metals, or water
- Temperature extremes, which reduce shelf life or cause freezing
- Evaporation, which can change the urea concentration
- Crystallisation, which blocks lines and injectors
Once DEF becomes contaminated or goes off-spec, it cannot be fixed and must be disposed of.
Ideal DEF storage conditions
To keep DEF usable and compliant, it should be stored under the following conditions:
Temperature Control
- Ideal storage temperature: -5°C to +25°C
- DEF freezes at -11°C but can be used again once fully thawed
- Prolonged exposure to high temperatures shortens shelf life
DEF shelf life varies depending on storage conditions — we explain this in more detail in how long does AdBlue last?.
Protection from sunlight
DEF should always be stored out of direct sunlight. UV exposure and heat can cause evaporation, reducing the urea concentration and affecting performance.
Dedicated, approved containers
DEF must be stored in containers made from compatible materials, such as:
- High-density polyethylene (HDPE)
- Stainless steel
It should never come into contact with copper, brass, zinc, or mild steel, as these materials cause contamination.
Using bunded AdBlue storage also protects against spills and environmental damage. Ace Plant offers a range of bunded AdBlue storage solutions designed specifically for site use.
Preventing DEF crystallisation and contamination
Crystallisation typically occurs when DEF is exposed to air, temperature fluctuations, or poor handling. Once crystals form, they can block pipes and injectors.
Good practice includes using sealed, dedicated dispensing equipment, cleaning nozzles regularly, and avoiding partial fills that allow evaporation. Ace Plant covers this in detail in how to prevent AdBlue crystallisation.
Common DEF storage mistakes to avoid
- Storing DEF next to diesel or other fuels
- Using shared pumps or funnels
- Leaving containers open or unsealed
- Ignoring temperature protection in winter
- Overfilling tanks without secondary containment
If DEF is accidentally added to a diesel tank, the fuel system must be drained and cleaned immediately to prevent serious damage.
Choosing the right DEF storage solution for your site
For construction and industrial sites, mobile and static bunded units are the safest option. Depending on space and usage, common solutions include:
For smaller quantities or containers, secure storage options like the Bundie Store, including the Bucket Bundie Store and Bunded Bundie Store, help prevent contamination and spills.
Real-world examples
Many contractors choose combined diesel and AdBlue units to simplify site logistics while keeping fluids fully separated. Examples include:
FAQs
Does DEF need to be stored separately from diesel?
Yes. DEF must always be stored in a dedicated container and never come into contact with diesel or fuel equipment.
Can DEF be used after freezing?
Yes. DEF freezes at -11°C and can be reused once fully thawed, as long as it hasn’t been contaminated.
What happens if DEF goes off-spec?
Off-spec DEF can cause SCR faults, reduced engine performance, or shutdowns and should not be used.
Diesel exhaust fluid does require special storage, but with the right equipment and handling, it’s easy to manage safely. Protecting DEF from contamination, temperature extremes, and sunlight ensures reliable machine operation, compliance with emissions regulations, and fewer costly disruptions on site.
For specialist advice or site-ready DEF storage solutions, Ace Plant offers a wide range of compliant, bunded options designed for real-world conditions. Get in touch today to discuss options for your DEF storage.