Fuel and Oil Separator Maintenance


Fuel and oil separators play a significant role in managing contaminated run-off and spills. If you don’t have the right type of separator or it’s poorly maintained, serious problems can occur.

The worst outcome is to see fuel or oil contaminate local waterways. The environment suffers of course, but so does your bottom line – the Environment Agency has a track record of issuing significant fines to businesses for failing to stop spills.

I’ve put together this guide about fuel and oil separators so you can make the right choice for your business and help to avoid costly mistakes.

I’ll start by explaining a bit about what separators do, how they work and the different types you can get, then move on to how to keep your separators/interceptors maintained to industry standards too.

What are fuel/oil separators and do how they work?

First of all, you might know separators as interceptors, which is their old name, so I am talking about the same infrastructure. Generally speaking, most separators in use today are single pots with coalescent filters and are used to collect and filter out fuel and oil found in surface water run-off from carparks, fuel station forecourts, vehicle muster points and so on.

Older infrastructure may use a slightly different kind of separator with a 3-chambered tank that filters contaminants into different chambers.

Whichever filtering system is in use the end goal is the same: the contaminants are contained in the separator and the water is released into drains, soakaways or sewers minimising any possible pollution.

When do you need to install a separator?

If your site has hard surfaces that will have oil or fuel contaminating the water run-off, it’s likely you’ll need to install a separator. There are different types for different scenarios, which I’ll explain below. Some examples of sites requiring a separator:

  • Vehicle muster points and maintenance areas
  • Roads
  • Industrial workshops
  • Refuelling facilities (including commercial and industrial forecourts)
  • Small car parks that discharge run-off into a sensitive environment such as a designated nature reserve or waterway
  • Car parks that have 50 or more spaces, or are larger than 800m2

Types of fuel/oil separators

There are three different types of separators. They all work in a similar fashion but are designed to cope with different volumes and contaminant requirements.

Bypass separator

These are designed for sites that have low rainfall and low risk of contaminant spills, like short term car parking, for example. Bypass separators work well for locations that experience water flows generated by rainfall, up to 6.5mm/hour.

bypass separator cutaway

These will cover around 99% of all rainfall events, but will allow heavier rainfalls to circumvent the separator (while processing as much as capacity will allow).

Full retention separators

These separators are built to handle much higher flows, up to 65mm/hr. Full retention separators are better suited to locations that experience very heavy rainfall, and/or a risk of high-volume spills.

full retention cutaway separator

Vehicle maintenance sites and heavy vehicle parking are locations which typically have this type of separator installed.

Forecourt Separator

This type of separator is best suited for refuelling sites and forecourts. They are designed to retain an entire fuel spill, up to the predicted maximum capacity of an on-site spill (usually the volume of a compartment of a fuel delivery tanker, or 7600 litres).

forecourt separator cutaway

What are the regulations around fuel/oil separators?

Fuel and oil separator installation and maintenance was regulated by the Environment Agency’s PPG3 document until December 2015. This has been withdrawn but still functions as good practice guidance in Northern Ireland, Wales and Scotland.

New regulatory framework will be released as GPP3 in the future. Additionally, the European standard EN858-2 is currently applicable in the UK as of the date this guide was written.

Separator maintenance requirements

The regulations above require inspections and separator maintenance to be conducted every 6 months. It’s absolutely necessary to service your separators and ensure they are cleared of accumulated build up regularly.

There are a number of tasks to be undertaken during separator or interceptor cleaning. The servicing should be conducted by an experienced team that has the appropriate training and safety qualifications.

Here’s a list of tasks you can expect a maintenance contractor to undertake during separator cleaning and servicing:

  • Inspect the integrity of the separator and all mechanical parts,
  • Inspect all filters and replace or repair as required,
  • Assess the amount of collected contaminants (oil and fuel) and silt,
  • Service any electrical systems including volume alarms and any interceptor management systems,
  • Inspect the coalescing device if installed, and replace if required,
  • Conduct safe silt/contaminant removal in accordance with waste transit and disposal regulations,
  • Install new separators to meet site and regulatory requirements,
  • Inspect supporting infrastructure such as gullies, manholes and pipework,
  • Maintain industry standard documentation,
  • Maintain logs of inspections, maintenance, incidents, services and contaminant removal.

What happens if separator maintenance isn’t carried out?

The consequences of failing to maintain separators can be severe. They are a key line of defence against fuel spills, so it’s in your company’s interest to have them in excellent condition.

The Environment Agency has taken legal action against companies that caused environmental damage due to poorly maintained separators. I’ve collected a few recent examples to give you an idea.

In 2010, VK Transport failed to empty their interceptor, which caused an overflow into a surface-level sewerage system. That system flowed directly into the River Thames. It resulted in fuel contaminating the river which caused significant environmental damage (not to mention the costs of the clean-up operation). They were fined £4,000 plus court costs.

Also in 2010, Thames Water was fined over £12,000 for two offences relating to poorly maintained separators. The pumps on the first separator had faulty sensors, which caused 4500 litres of diesel to spill into a waterway. The second interceptor’s drain became blocked with silt which caused another spill (of raw sewerage in this case).

In 2014, company Eco Oil was fined £30,000 for allowing a spill to occur in 2012. The separator was overwhelmed by heavy rain, which caused the collected contaminants to overflow into a drain which let out into the River Orwell.

Additionally, the volume sensors had been decommissioned because they hadn’t been working properly. The fuel spread 4 miles downriver, contaminating sensitive environmental areas, and killed wildlife.


The issues and subsequent fines highlighted above, could easily have been avoided if proper maintenance had been conducted. It’s a good reminder to inspect your separators regularly, and have them serviced or emptied as required in addition to your biannual inspections. By doing so you will not only protect your finances but also the environment.

How Can Octane Help?

Octane offers safe and reliable separator cleaning and maintenance services. We carry out all services to both UK and EU regulation standards, and include detailed logbooks and documentation.

Our service personnel are experienced, and have SPA Safety Passports alongside specialist skillsets, first aid and safety awareness training. If you’d like to know more about what we offer, please contact us today on 0113 2012 460

Jason Unsworth is a Director of Octane Holding Group Ltd and has worked in the refuelling system services industry for over 20 years. Jason is responsible for all operational aspects of Octane Holding Group Ltd. and when he's not working he has a keen interest in motorsport , riding his motorbike and enjoys spending time with his grown up children.