Trade Waste Requirements NSW: Permits, Pre-Treatment and Compliance

What You Need to Know

Trade waste is any liquid waste discharged to the sewer that is not domestic sewage. If your business produces wastewater from food preparation, vehicle servicing, dental procedures, medical activities, commercial laundry, or hairdressing, that discharge is classified as trade waste under NSW law. You cannot legally discharge it without a trade waste agreement from your water utility.

In the Sydney Water service area, every business generating trade waste must hold a valid agreement before any discharge occurs. There are three agreement categories: concurrence (for new developments or change of use during the DA or CDC process), consent (for ongoing discharges from existing premises), and permits (for specific lower-risk or short-term activities). The type you need depends on whether you are building new, fitting out, or already operating.

Pre-treatment is mandatory for most trade waste types. A restaurant needs a grease arrestor. An automotive workshop needs an oil and sediment separator. A dental surgery needs a plaster trap and amalgam separator. The equipment must be correctly sized, properly installed, and regularly maintained. Failure to comply can result in fines up to $44,000 per offence, sewer disconnection, and remediation orders.

A hydraulic engineer designs the trade waste pre-treatment system, sizes the equipment, coordinates with Sydney Water for approval, and certifies that the installation meets AS 1547 and AS/NZS 3500 requirements. Getting this right at design stage avoids costly retrofits and delays to your occupation certificate.

• All trade waste discharges require a Sydney Water trade waste agreement. Operating without one is an offence under the Sydney Water Act 1994 and the Sydney Water Regulation. Penalties apply per offence per day. (Sydney Water Act 1994, s 50)
• Pre-treatment must comply with AS 1547 (on-site domestic wastewater management). This standard covers grease arrestor sizing, oil separator design, and general pre-treatment requirements. Sydney Water's trade waste policy references AS 1547 as the baseline for equipment sizing. (AS 1547:2012)
• All plumbing and drainage must comply with AS/NZS 3500. Trade waste pre-treatment equipment connects into the sanitary drainage system and must meet Part 2 (sanitary plumbing and drainage) requirements for pipe sizing, grading, venting, and access. (AS/NZS 3500.2)
• Food businesses must install grease arrestors sized to peak flow. Sydney Water requires in-ground grease arrestors for most food premises. Above-ground passive grease traps are only accepted for very low-volume applications such as small tea rooms or office kitchenettes with no cooking. (Sydney Water Trade Waste Policy)
• Automotive and industrial premises must install oil and sediment separators. These must be sized for the catchment area and expected contaminant load. Coalescing plate separators are generally required for automotive workshops. (Sydney Water Trade Waste Policy, AS 1547)
• Dental practices must install plaster traps and amalgam separators. Plaster traps capture gypsum from dental impressions. Amalgam separators capture mercury-containing waste. Both are mandatory before discharge to sewer. (Sydney Water Trade Waste Policy)
• Cooling tower blowdown is classified as trade waste. The chemical treatment used in cooling towers (biocides, corrosion inhibitors, scale inhibitors) means blowdown water cannot be discharged as domestic sewage. A trade waste agreement is required. (Sydney Water Trade Waste Policy)
• Sydney Water may require sampling and monitoring. For higher-risk discharges (Category 2 and 3), ongoing sampling, testing, and reporting may be conditions of the trade waste agreement. The frequency and parameters depend on the discharge type and volume. (Sydney Water Trade Waste Policy)

The most common trade waste scenario is a food business. Every restaurant, cafe, bakery, takeaway shop, hotel kitchen, and commercial kitchen in a strata building needs a grease arrestor. Sydney Water does not accept alternatives for premises that cook food. The arrestor must be in-ground, externally located where possible, and sized based on peak flow rates and the number of fixtures draining through it.

Grease arrestor sizing follows AS 1547 methodology. A small cafe with a single-bowl sink and one dishwasher might need a 1,000 litre arrestor. A large restaurant with multiple sinks, a commercial dishwasher, and a wok station could require 2,500 to 5,000 litres. The hydraulic engineer calculates the size based on fixture unit counts, simultaneous use factors, and the type of food preparation. Undersizing causes blockages, odour complaints, and non-compliance. Oversizing wastes money on excavation and equipment.

Automotive workshops generate oil, grease, detergents, and heavy metals in their wash water. An oil and sediment separator is required for any area where vehicles are washed, serviced, or repaired. The separator must include a sediment settling chamber, an oil separation chamber, and in most cases a coalescing plate pack for finer separation. Floor drains in service bays must drain to the separator, not directly to sewer. Car wash bays and detailing areas also require pre-treatment.

Dental practices produce two distinct waste streams that need separate treatment. Plaster traps capture gypsum and calcium sulphate from impression and model work. Amalgam separators capture mercury-containing particulate from old fillings. Both devices must be installed upstream of the connection to the building drainage system. Plaster trap sizing is based on the number of dental chairs and the volume of impression work. Most practices need a 20 to 40 litre plaster trap and an ISO 11143-compliant amalgam separator.

Medical and pathology laboratories discharge chemicals, biological agents, and pharmaceuticals. These require specific pre-treatment depending on the substances involved. Sydney Water assesses each laboratory individually. Common requirements include neutralisation tanks for acid/alkaline waste and holding tanks for batch discharge of concentrated waste.

Commercial laundries discharge water containing lint, detergents, bleach, and fabric softeners. A lint trap is the minimum pre-treatment requirement. Large laundries processing more than 10 tonnes of linen per week may need pH correction and temperature reduction before discharge. Laundries serving hospitals or aged care facilities may also need disinfection compliance checks.

Hairdressers and beauty salons produce waste containing hair, dyes, peroxide, and chemical treatments. A hair and lint trap is required on all basin wastes. For salons with high-volume chemical processing (such as hair colour specialists), Sydney Water may require additional pre-treatment or sampling.

Cooling tower blowdown is often overlooked as trade waste. Every cooling tower uses chemical treatment to control legionella, corrosion, and scale. When the tower bleeds off concentrated water, that blowdown contains elevated chemical levels that exceed domestic sewage limits. The trade waste agreement for cooling tower blowdown specifies acceptable concentration limits for biocides, conductivity, and pH. The mechanical engineer and the hydraulic engineer must coordinate on this, particularly in buildings where the cooling tower serves a large chilled water system.

In strata and multi-tenancy buildings, trade waste gets complicated. Each food tenant needs their own grease arrestor, but the building drainage system must accommodate all of them. The body corporate or building owner holds the overarching trade waste agreement with Sydney Water, but individual tenants are responsible for maintaining their pre-treatment equipment. The hydraulic design must allow for future tenant changes. A space designed as a retail shop today could become a restaurant tomorrow. If the drainage does not include provisions for a grease arrestor connection, the fitout cost for the new tenant increases significantly.

Sampling and monitoring apply to higher-risk trade waste categories. Sydney Water classifies trade waste into three categories based on risk. Category 1 (low risk, such as hairdressers) typically requires only pre-treatment and annual inspections. Category 2 (medium risk, such as restaurants) may require quarterly sampling. Category 3 (high risk, such as industrial processes) can require monthly sampling, continuous monitoring, and detailed reporting. Sampling costs $500 to $2,000 per event depending on the parameters tested.

Penalties for non-compliance are significant. Sydney Water can issue penalty infringement notices of up to $44,000 per offence. They can also require remediation works, install monitoring equipment at the business owner's cost, restrict or disconnect the sewer connection, and recover costs for any damage to the sewer network caused by non-compliant discharges. In serious cases, the EPA can also take action under the Protection of the Environment Operations Act 1997.