Oil-water separators help treat oily condensate from oil-injected compressed-air systems before disposal. They are an important part of environmental control — but compliance depends on correct sizing, maintenance, lubricant compatibility and the final discharge route.
Compressed-air systems draw moisture and airborne contamination into the compression process. As the air cools, water condenses in receivers, dryers, filters and pipework. In oil-injected systems, that condensate can also contain lubricant.
Businesses must manage contaminated water so it does not cause pollution. GOV.UK guidance says contaminated water should be reused, treated, removed by a registered waste carrier, or discharged to a foul or combined sewer only where the relevant permission is in place.
Not every compressed-air installation has the same legal or technical solution. An oil-water separator is often a practical treatment method for oily compressor condensate, but the correct route depends on the site.
The old article quoted a fixed £20,000 fine and suggested imprisonment in broad terms. That wording is too simplistic. Environmental offences and trade-effluent breaches can result in enforcement action and financial penalties, but the applicable offence, court, penalty and liability depend on the circumstances and current law.
For practical compliance, the more important point is this: contaminated water must not be allowed to cause pollution, and trade-effluent discharges to sewer require the correct consent or agreement with the sewerage undertaker.
A compressed-air oil-water separator treats the condensate leaving the compressed-air system. It does not clean the compressed air being supplied to tools or machinery.
Free oil can be separated and residual oil can be captured using coalescing, adsorption or specialist media depending on the separator design.
Dryers and compressed-air filters are used to improve the air supplied downstream. An oil-water separator sits on the condensate-disposal side of the system.
The previous page stated that oil-water separators remove up to 99.5% of oil and therefore ensure clean discharge. Performance varies by separator design, lubricant chemistry, condensate loading, maintenance condition and operating environment.
Some current Tanair products are designed to achieve less than 10 ppm residual oil under suitable conditions. That specification is more useful than a generic percentage, but it still does not automatically grant permission to discharge the treated water.
The live page currently carries a wide range of Tanair condensate systems from compact workshop units through to high-capacity models for larger multi-compressor installations. These useful product routes are retained below.
| Selection Factor | Why It Matters |
|---|---|
| Total compressor capacity | Provides the baseline flow reference for the separator. |
| Operating hours | Longer running hours increase condensate and oil loading. |
| Lubricant type | Mineral, synthetic and polyglycol lubricants can behave differently in condensate. |
| Ambient humidity | Higher moisture levels can substantially increase condensate volume. |
| Number of compressors | Combined condensate load must be considered where several machines share one separator. |
| Drain arrangement | Receivers, dryers and filters can all contribute condensate. |
| Required discharge standard | The separator needs to suit the consent, agreement or waste route applying to the site. |
Not all compressor oils separate from water in the same way. Stable emulsions and some synthetic lubricants can be harder to treat with conventional separator media.
The old article presented 4,000 hours as though every separator has the same working life. Some current Tanair media is rated up to that figure, but service life depends on the actual model and application.
Contaminated water must be managed so it does not cause pollution. Discharge to sewer can require trade-effluent consent or an agreement, while discharge to surface water or ground can require environmental permission depending on the circumstances.
Do not assume so. Surface-water drains can discharge directly to the environment, and contaminated or trade-effluent discharges can require an environmental permit or another authorised route.
No. It is a treatment device. Compliance also depends on correct sizing, media condition, lubricant compatibility, treatment performance and the final permitted discharge or disposal route.
No. They treat waste condensate after it leaves the compressed-air system. Dryers and compressed-air filters treat the air supplied to equipment.
There is no universal percentage. Use the performance specification for the exact separator under the stated operating conditions.
Follow the exact product's service guidance. Some media may be rated up to a stated number of operating hours, but actual life depends on condensate load, lubricant and operating conditions.
Yes, where the separator is sized for the combined condensate load and the lubricant types are compatible with the treatment media.
Yes. Send the compressor make and model, combined airflow, lubricant type, operating hours and proposed condensate-disposal route so the treatment system can be assessed.
Tell us your compressor capacity, lubricant type, operating hours and where the condensate currently drains. We can help identify a suitable separator and replacement media.
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