Gross Pollutant Traps

A Gross Pollutant Trap (GPT) is the first line of defence in a stormwater treatment system and removes much of the bulky pollutants from stormwater runoff. Categorized as primary treatment devices, GPTs (Gross Pollutant Traps) are commonly used to fend off litter, cigarette butts, plastic bottles, leaves, and sediment.



Pollution captured by GPT systems is prevented from conveyance through catchment areas, capturing it before it reaches our rivers and ocean environments. Gross pollutants, including plastic pollution, are removed from our drains and subsequent parts of our water network.

GPTs can be installed independently, or as stormwater pre-treatment that work in conjunction with secondary and tertiary devices. They are often used to compliment stormwater devices downstream, which work together to secure better water quality outcomes.

GPTs play a key role in primary treatment. This ensures secondary and tertiary treatment devices such as biofilters, raingardens and proprietary filters, can ‘polish’ or clean stormwater without being blocked by larger pieces of rubbish and debris.


There are several different GPTs in the market today – all removing gross pollutants from our stormwater system in different ways. Most GPTs fall into one of the below categories:

    • Difference in specific gravity traps – systems which use gravity to separate pollutants that float and settle without the use of screens. Water quality is achieved by incorporating baffles/booms in a series of chambers.
    • Direct screening – devices which incorporate screens in various orientations to manage the flow. These are not self-cleansing.
    • Vortex type devices – devices that direct flow to produce vortices/hydrodynamic separation, but do not have a screen.
    • Devices that combine a vortex or hydrodynamic separation with a non-blocking screening system – these are known as ‘continuous deflective separation’ units. The SPEL Vortceptor GPT is a vortex separation unit with a non-blocking screen system.


Highly engineered water quality devices, deployed directly into the stormwater system to capture contaminants close to the surface.


A vertically configured pollutant trap suitable for low risk applications. 

Baffle Box

Concrete or fibreglass structures containing a series of sediment settling chambers separated by baffles.


Non-blocking hydrodynamic separator with a unique screen and treatment action, resulting in excellent pollution removal performance and high water quality outcomes.


The SPEL Hydrochannel is a WSUD drainage system, offering a decentralized and absolutely new path for stormwater treatment.

Gross Pollutant Traps

Case studies, webinars, projects and media.

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