Flowco Global

Introduction

Phase separation in E10 petrol is one of the most misunderstood but costly risks facing fuel operators in Australia. Often mistaken for “just water in the tank”, phase separation is a chemical breakdown that can shut down dispensers, damage engines, and create serious compliance issues.

At Flowco Australia, we are seeing more phase separation cases across retail fuel sites. This page explains what phase separation is, why it’s increasing, the risks it poses, and how to protect your business.

What is Phase Separation in E10?

E10 is a blend of petrol with up to ten percent ethanol. Ethanol naturally absorbs water, but only to a limit. Once saturated, the fuel separates into two layers:

Top Layer (Ethanol-Lean Petrol): Reduced octane, off-specification, and unstable.
Bottom Layer (Ethanol-Water Mix): Dense, corrosive, and highly damaging to engines.

If the ethanol-water layer is drawn into pumps or engines, it leads to sudden failures, shutdowns, and customer complaints.

Why Phase Separation Happens

Several common conditions make phase separation more likely:

Temperature cycles causing condensation inside tanks
Water ingress through lids, manways, spill buckets, or damaged seals
Low fuel turnover leaving E10 in tanks for extended periods
Moisture in deliveries from the supply chain
High humidity and rainfall in coastal and tropical climates

Risks for Fuel Operators

Phase separation is more than a fuel quality problem — it affects operations, finances, and compliance.

Retail Fuel Forecourts

Sudden water alarms and pump shutdowns
Blocked dispenser filters and slow flow
Customer complaints about drivability
False ATG water readings
Repeat callouts until the root cause is addressed
Reputational and brand damage

Marine, Agricultural & Small Engines

Stalling, hard starting, and misfires
Pump, injector, and carburettor damage
Poor reliability of equipment during critical use

Damage to Tanks and UST Equipment

The ethanol-water layer formed during phase separation is highly corrosive. Left untreated, it can:

Accelerate corrosion on steel tank bottoms and fittings, leading to pitting and structural weakness.
Attack protective coatings on tank interiors, exposing bare metal and increasing long-term integrity risks.
Degrade pipework and risers, particularly where moisture collects, resulting in leaks and potential environmental contamination.
Compromise submersible pumps, sensors, and probes, as corrosive ethanol-water solutions damage seals, wiring, and electronic components.
Cause false ATG readings when probes become coated with corrosive deposits, masking true water levels or triggering nuisance alarms.

This type of infrastructure damage can transform what begins as a fuel quality issue into a much larger compliance and environmental liability, including costly repairs, regulatory reporting, and potential tank replacement.

Financial & Compliance

Lost sales and downtime
Emergency service callouts and disposal costs
Fuel write-offs when product is off-spec
Non-compliance with AS 4897 and AS 1940 standards
Risk of EPA involvement if structural corrosion results in leaks to soil or groundwater

Warning Signs of Phase Separation

Water alarms triggered after rain or deliveries
Frequent filter replacements with little improvement
Customer reports of poor engine performance
Visible water-rich layer in fuel samples
ATG readings inconsistent with manual water checks

Flowco’s 5-Step Remediation Process

Flowco provides end-to-end solutions to detect, resolve, and prevent phase separation in E10 tanks:

Assessment & Sampling – Fuel testing, water paste checks, and ethanol content analysis.
Containment – Isolating affected lines and pumps to protect customers.
Layer Removal – Safe extraction of the ethanol-water phase at the tank bottom.
Fuel Restoration – Polishing and rebalancing usable fuel, or uplifting and replacing off-spec product.
Prevention & Monitoring – Repairs to lids and seals, delivery procedures, and scheduled water checks.

Or see understand our process by watching a detailed animation here.

Best Practices for Operators

Inspect tanks regularly with water paste
Maintain gaskets, lids, and spill containers
Avoid long storage times on E10 grades
Train staff to escalate early warning signs
Use ethanol-compatible components
Schedule preventive water management checks

Conclusion: Protect Your Fuel Quality and Your Business

Phase separation in E10 is a growing challenge for operators across Australia. Left unchecked, it can quietly degrade fuel quality until it suddenly forces your site offline.

Flowco Australia delivers nationwide fuel assessment, tank cleaning, and water management programs. With advanced equipment, trained technicians, and expertise in AS 4897 and AS 1940 compliance, we help operators stay ahead of fuel quality risks.

Don’t let phase separation take your site offline — contact Flowco today to book a site assessment.

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Phase Separation in E10 Petrol – Tank Cleaning and Fuel Polishing