Where condensate comes from
Air drawn into a compressor carries water vapour. As the air is compressed and cooled, the vapour condenses in aftercoolers, receivers, dryers, filters and low points of the piping. Where the compressor is oil-injected, the condensate carries some lubricant, and in some systems it also carries dust and corrosion products.
Why it needs treatment
Condensate is a problem because:
- Oil in the discharge can breach local environmental and wastewater requirements
- Lubricant types differ, and some form stable emulsions that are hard to separate
- Untreated discharge can damage drains and the surroundings
- A failed separator quietly lets contaminated water leave the site
How oil-water separators work
Most separators use gravity and filtration stages. Condensate first passes through a stage that lets the oil separate from the water, and then through media, often activated carbon or similar, that capture remaining oil. The separated oil is collected for proper disposal and the treated water is discharged where permitted.
Selection depends on
Points that decide the right equipment:
- The compressor type and lubricant, including synthetic fluids that emulsify
- The condensate flow, which depends on air flow, humidity and temperature
- The local discharge requirement, which varies by authority
- The location, access for servicing and the disposal route for collected oil
Keep it reliable
Reliability practices:
- Make sure drains actually deliver condensate to the separator and are not left blocked or open
- Inspect the separator and replace media on a schedule, not only after a problem
- Check the condition of the treated water against the requirement you must meet
- Record inspections and disposal of the collected oil
- Protect the unit from freezing, overload and contamination from other sources
Our approach
We help you identify the condensate sources, choose a separator that suits the lubricant and the flow, and set a maintenance routine. We do not state the discharge limit that applies to your site, because it depends on your local authority and licence, and you should confirm it with them.
Frequently asked questions
Can I discharge compressor condensate to the drain?
Only if the discharge meets the requirement set by your local authority or wastewater operator. Condensate containing oil usually needs treatment first.
Why is my separator not working well with synthetic oil?
Some synthetic lubricants form emulsions that ordinary gravity separators handle poorly. The separator should be chosen to suit the lubricant.
How often should the filter media be changed?
It depends on the condensate flow, the oil content and the unit. Follow the manufacturer's schedule and test the treated water.
Is condensate from an oil-free compressor safe to drain?
It may still contain contamination from the intake air and the piping, so it should be assessed against the local requirement.