The wastewater from mechanical workshops can contain contaminants such as fuels, solvents, heavy metals, battery acids, flammable substances, caustic cleaners, coolants, paints, fillers, grit and residue. If not properly managed, this wastewater can pollute our waterways, damage our sewer systems and wastewater treatment facilities and affect the health and safety of sewerage system workers.

Legal requirements for all mechanical businesses

  • Obtain a trade waste approval.
  • Be subject to regular audits from trade waste officers who will advise on trade waste issues and ensure compliance under the Water Supply(Safety & Reliability) Act 2008,Trade Waste Policy and Trade Waste Management Plan (TWMP).
  • Any business found not to be compliant with the relevant legislation and policy requirements will be required to upgrade their present facility to meet the minimum standards.

Treatment and disposal of liquid wastewater options

You will need to determine what best suits your business. Outlined below are the options for the treatment and disposal of liquid wastewater generated by your business. 

  1. Dry process (hand washing only).
  2. Onsite recycle or collection of wastewater.
  3. Wastewater is discharged to sewer via our approved pre-treatment process.

1. Dry process

A dry process means the work area is not connected to sewer or stormwater systems and the workshop operates without a floor drain or wash bay. This method poses the least risk to the sewerage system and saves you the cost of complying with our minimum standards for pre-treatment.

The business must:

  • Obtain a current trade waste approval.
  • Ensure that soiled hands from working in a mechanical environment are only washed over an approved hand washbasin, which discharges to sewer. Do not wash hands under any other tap or hose (internal or external of the premises).
  • Clearly sign the washbasin dedicated to wash hands soiled from business activities.
  • Install bunds to repel rainwater and prevent accidental spills escaping to the sewer or stormwater system. (Our minimum bunding specifications apply)
  • Only mop or sweep floors. Do not use a hose.
  • Make sure vehicles are completely inside the bunded area before commencing any work.
  • Wash engines parts in an approved parts washer (recycler).
  • Not wash vehicles, equipment, engine bays etc.
  • Wipe up spills immediately using absorbent materials.
  • Use trays to collect drips of oil etc from the vehicle.
  • Install a bund around oil storage areas to prevent oil spills and other liquids entering the sewer stormwater system.
  • Capture and store separately radiator fluids waste brake fluids, motor oils, solvents, paints,degreasers and fuels in drums for collection by an EPA approved Licensed Liquid Waste Transport Operator.
  • Store batteries in a bunded area on top of a plastic pallet. Do not store batteries containing acid outside the workshop. Accidental waste and spills in this area should drain to a blind sump and not be allowed to discharge to sewer or stormwater systems. Batteries should be removed for recycling as soon as possible.

2. On-site systems for the collection or recycling of wastewater

Any business where liquid waste is generated from a trade or manufacturing process and then released to a sewer system will be required to comply with our trade waste policy and trade waste plan. However, exemptions to requirements to have pre-treatment facilities and equipment may be given where wastewaters are collected onsite and not released to a sewer or stormwater system. This means that all wastewaters generated from wash bays or parts washing sinks within workshops or similar commercial activities are to be collected into appropriately sized holding tanks for collection and eventual disposal by an approved and licensed liquid waste transport business. No wastewaters are to be released or connected to a sewer system with the exception to that which is generated from an approved hand wash basin.

The business must:

  • Obtain a current trade waste Approval, which will only permit the discharge to sewer of wastewater generated from washing hands.
  • Ensure that any wastewater contained onsite complies with the relevant conditions of the business’s Environmentally Relevant Activity (ERA) license.
  • If the business does not have a current ERA license and conducts any washing activity onsite where the wastewater is contained and not connected to sewer, it may be required to apply for an ERA license.
  • Ensure that the amount of regulated waste stored onsite complies with the relevant licensing requirements and the approved use for the premise.
  • Make sure that with the exception of hand washing, staff amenities and toilets, no wastewater generated by the business is discharged to the sewer, and that no wastewater is discharged to the stormwater system.

Waste water holding tank

Once the wastewater is contained onsite in a holding tank and no connection or release is made to the sewer, it is no longer to be considered as a trade waste. It may instead be classed as a regulated waste under Environmental Protection legislation and may affect a current Environmental Licence (Environmentally Relevant Activity - ERA license) or require a business to obtain an ERA licence. Should you decide to implement an onsite system for collecting wastewater it is advisable that you make contact with our Environmental Health Branch to discuss any ERA licensing conditions or requirements that might apply to your operations.

The capacity of any holding tank will need to be carefully considered to ensure that it can be effectively serviced to meet the needs of your business. Other measures should also be implemented to ensure your obligation to prevent overflows or releases to stormwater or the environment is met (i.e. General Environmental Duty).

Stored amounts of regulated waste

The storage of large amounts of regulated waste on-site may trigger a change in the material use of a premise from that which it has previously been approved. For further information regarding the storage of large amounts of regulated waste you are advised to contact the relevant administering authorities including; the Department of Environment and Resource Management (DERM), our Development Assessment and Environmental Health Branches.

3. Discharge liquid wastewater to sewer

Discharge to sewer means the work area is connected to sewer but not connected to stormwater systems. This method requires pre-treatment devices to be installed and compliance with discharge conditions. A pre-treatment device is required to reduce the quantities of silt, oil, grease, and petroleum hydrocarbons entering the sewer.

The business must:

Obtain a trade waste approval which will allow all liquid waste generated by the business to be discharged to sewer provided all pre-treatment requirements are installed and sewer admission limits are maintained.

  • Install a trade waste sub water meter/meter(s).
  • Ensure that effluent from the pre-treatment devices drains only to sewer and not to stormwater systems or the environment.
  • Ensure that all stormwater is to be discharged to stormwater, not to sewer. Pre-treat wastewater before discharge to sewer to comply with the standard sewer admission limits.
  • Install a wash bay facility (must comply with our minimum standard requirements). Separate advice sheets are available on request from our Trade Waste Services.
  • Ensure pre-treatment devices are serviced regularly in accordance with the manufacturer’s recommendations and our set minimum service requirement.
  • Use pressure cleaners and quick break detergents (rated to break within 15 minutes separation time) to wash floors, large parts and engine bays.
  • Wipe up spills immediately, place trays under leaking parts and use a pressure spray to wash the floor within the defined wet area.
  • Do not drain neat fuel or neat oil to a pit that is pumped to the sewer via an oil/water separator.
  • Capture and store separately coolants, brake fluid, motor oil and fuels in drums for off site removal by an EPA approved Licensed Liquid Waste Transport Operator.
  • Do not store batteries containing acid outside. Store batteries in a bunded area on top of a plastic pallet. Accidental waste and spills in this area should drain to a blind sump and not be allowed to discharge to sewer or stormwater systems. Batteries should be removed off site for recycling as soon as possible.
  • Wash small parts in a solvent based recycling parts washer.Do not discharge chemical bath liquids directly to sewer. Instead, arrange for an EPA approved licensed liquid waste transport operator to remove chemical bath liquid off site.
  • Ensure that soiled hands from working in a mechanical environment are only washed over an approved hand washbasin, which discharges to sewer. Do not wash hands under any other tap or hose (internal or external of the premises).
  • Clearly sign the washbasin dedicated to wash hands soiled from business activities. 

Contaminant sewer limits

  • Silt (as suspended solids) - 500 milligrams per litre
  • Total oil and grease - 200 milligrams per litre
  • Petroleum hydrocarbons - 30 milligrams per litre

Related documents

Liquid trade waste application form (online)

Trade waste liquid discharge - category 2 form (PDF for print)

Trade Waste Management Plan

2.54 Trade Waste Policy