Discharging compressed-air condensate: the standards in Québec
The condensate drained from a compressed-air system is a mix of water and oil. From a lubricated compressor, it can carry oil at several hundred to several thousand mg/L — far beyond what a sewer accepts. It therefore cannot be discharged untreated: an oil/water separator is required before discharge.
Key point — for compressed-air condensate, the relevant regulatory parameter is C10-C50 petroleum hydrocarbons (mineral lubricating oil), not “total oil and grease” (which targets food, vegetable or animal fats).
Notice. This sheet is provided for information only and does not constitute legal advice. Discharge limits are municipal and may change; it is each operator’s responsibility to verify the requirements in force at their workplace with their municipality and the competent authorities.
A municipal standard, not a provincial one
Oil discharge limits are set by municipal bylaw, and so vary from one city to the next. Two common misconceptions to correct:
- The ROMAEU (Q-2, r. 34.1) sets no limit on oil or hydrocarbons: it covers only cBOD5, TSS, pH and toxicity at the outlet of treatment plants, and it applies to the municipal operator — not to the industrial discharge.
- The REAFIE (Q-2, r. 0.1) governs stormwater management through ministerial authorization, but sets no universal chemical threshold for hydrocarbons.
The most widely used reference value, 15 mg/L of C10-C50 to the domestic sewer, comes from the MELCCFP model bylaw, a template adopted by many municipalities. Always check your own municipality’s bylaw for the applicable limit and discharge point.
The limits in Québec City (R.A.V.Q. 1124)
Across the Québec City agglomeration (including L’Ancienne-Lorette and Saint-Augustin-de-Desmaures), bylaw R.A.V.Q. 1124 sets, for C10-C50 petroleum hydrocarbons:
| Discharge point | C10-C50 hydrocarbons — maximum |
|---|---|
| Domestic or combined sewer | 15 mg/L |
| Storm sewer or watercourse | 3.5 mg/L |
The stricter storm-sewer limit reflects the fact that this network discharges directly to the environment, without passing through a treatment plant.
The operator’s obligations
- Oil/water separator (s. 6): any business liable to discharge mineral, lubricating or other hydrocarbons must install an oil/water separator compliant with the ministry’s Guide sur les séparateurs eau-huile, and maintain it.
- No additives: it is prohibited to add emulsifiers, enzymes, bacteria, solvents or hot water to flush oil into the sewer.
- Discharge permit (s. 18): an industrial establishment discharging process water must obtain a discharge permit from its borough.
- Records: keep proof of maintenance and residue disposal for 5 years.
- Characterization (s. 22): a report supervised by a competent person (engineer, chemist or technologist) is required above 10,000 m³/year of effluent.
Choosing treatment by discharge point
| Discharge point | Target | Typical equipment |
|---|---|---|
| Sanitary / domestic sewer | ≤ 15 mg/L | Gravity or lamellar separator |
| Storm sewer or watercourse | ≤ 3.5 mg/L | Separator + activated carbon, or emulsion splitting (targeting < 5 mg/L) |
In practice: a gravity separator with activated carbon is usually enough to meet the 15 mg/L domestic-sewer limit; heavily emulsified condensate (screw compressors with certain oils) or a storm-sewer discharge calls for more advanced treatment. Prefer connecting to the domestic sewer: the limit is more permissive and the ministry’s Guide recommends that discharge point.
For equipment, see our oil/water separators (gravity, high-efficiency and emulsion splitting) and our zero-air-loss condensate drains. To reduce the upstream water and oil load, see also Water in the compressed-air system.
Elsewhere in Québec
Outside the Québec City agglomeration, the limit and method differ: Montréal applies the CMM bylaw (2008-47), while Lévis and other cities have their own. The common baseline remains the MELCCFP model (15 mg/L of C10-C50 to the domestic sewer), but always confirm with the relevant municipality before designing the installation.
Onyx M3 offers selection support for condensate-treatment equipment matched to your discharge point and municipality — even if you don’t buy the equipment from us. Request a free consultation.
References
- Bylaw R.A.V.Q. 1124 (Québec City agglomeration) — text and Schedule I
- Ville de Québec — Industrial discharge to the sewer
- MDDEP — Guide on oil/water separators (2008)
- MELCCFP — Model bylaw on discharges to sewer networks
- ROMAEU — CQLR c. Q-2, r. 34.1
The thresholds reflect R.A.V.Q. 1124 as consolidated to 15 May 2026. Regulations may change; check the most recent official version and confirm the requirements specific to your installation with your municipality.