Oil-water separators for compressed air systems

Lawful and efficient disposal of compressed air condensate

Environmental regulations strictly prohibit the discharge of oily waste and chemicals in the water cycle. Under the Water Resources Act 1991, releasing noxious or polluting material into drains carries fines of up to £20,000. Compressor condensate falls under this legislation because it contains a mixture of water and oil and is therefore classified as hazardous industrial waste.

Untreated condensate cannot legally be discharged into foul sewers or the environment.

Read Government guidance on the legislation surrounding the Water Resources Act.

When air is compressed, it becomes saturated with water vapour. As the air cools, this vapour condenses into liquid. At the same time, small amounts of compressor lubricant vaporise during operation and mix with the water. The result is a dirty, oily condensate that must be disposed of responsibly - either collected by a licensed waste carrier or treated at source.

An oil-water separator (OWS) provides a practical, compliant, and cost‑effective solution. The device collects condensate from your compressor, tank, filters, and dryer, then separates the oil from the water using techniques such as adsorption, absorption, and gravitational or mechanical separation. Once treated, the cleaned water - containing almost no residual oil - can be safely discharged into the site’s wastepipe, eliminating the need for costly off‑site disposal.

Oil-water separators are not optional add‑ons. They are a core part of responsible compressed air system design and environmental management.

Convenience

Oil-water separators are simple to install and easy to maintain. By treating condensate on site, you reduce your reliance on external waste‑collection providers and avoid the administrative burden of arranging regular pickups. This gives you greater control, reliability, and operational flexibility.

Environment

Even small quantities of oil can contaminate large volumes of water, harming aquatic life, damaging vegetation, and causing long‑lasting environmental impact. Oil in wastewater can also clog or damage drainage infrastructure and contribute to wider pollution issues.

Treating condensate in‑house is a more sustainable and energy‑efficient approach than transporting hazardous waste off‑site. Oil-water separation is not only a legal requirement - it is the right thing to do for the environment.

Cost Efficiency

Compressor condensate is typically around 95% water. Disposing of it untreated means paying hazardous waste charges on the full volume, making off‑site disposal unnecessarily expensive. By removing the oil at source, an OWS dramatically reduces the volume of waste that must be handled as hazardous.

 In addition, untreated condensate can cause contamination and corrosion within the compressed air system. Effective oil removal helps prevent damage to drains, pipework, and downstream equipment -reducing repair costs and extending component life.

And of course, compliance protects you from costly enforcement action and reputational damage.

For any business using oil‑lubricated compressors, installing an oil-water separator is a practical, cost‑effective step that delivers long‑term operational, financial, and environmental value. It is both a legal obligation and a smart investment in the future of your site, your equipment, and the environment.

BCAS supplies a wide range of oil-water separators and can advise on the best option for your compressed air set‑up.

To find out more,  contact the BCAS team.