Vortex Separators

Frequently Asked Questions

What is a vortex separator? A vortex separator (also called a hydrodynamic separator) is an underground stormwater treatment chamber that uses the spinning motion of water to remove sediment, silt, and other solid pollutants before they reach a watercourse or soakaway. As water enters the chamber, it's forced into a rotating flow pattern that pushes heavier particles to the outer edge and down into a sump, while cleaner water continues through the outlet. How does the Stormshark Advanced Hydrodynamic Vortex Separator work? The Stormshark uses a patented internal design to create a controlled vortex that separates sediment-bound pollutants from surface water runoff without moving parts or external power. It's built for use within a SuDS (Sustainable Drainage System) treatment train, giving certainty over water quality before discharge and helping protect downstream controlled waters, amenity space, and biodiversity. What sizes of vortex separator are available? The Stormshark range runs from 750mm up to 3000mm in diameter, covering pipework diameters from 150mm through to 900mm. This spread means there's a suitable unit for anything from a small residential development to a large commercial or industrial site with high flow volumes. Where are vortex separators used? Vortex separators are typically installed as part of a SuDS treatment train on housing developments, commercial sites, car parks, solar farms, data centres, and highways schemes — anywhere surface water runoff needs to be treated for sediment and pollutants before it's discharged to a soakaway, watercourse, or the public sewer. Do I need a vortex separator for planning or SuDS compliance? Many local authorities and water companies now require a defined level of water quality treatment as part of SuDS approval, particularly where runoff discharges to a sensitive watercourse. A hydrodynamic separator like the Stormshark is a recognised way of providing that treatment stage within a wider drainage strategy, though the exact requirement depends on your site, drainage strategy, and the relevant SuDS approving body — check your specific requirements with your drainage engineer or local SuDS approval body. What's the difference between a vortex separator and a full retention or bypass separator? Full retention and bypass separators (sometimes called oil/petrol interceptors) are designed primarily to capture free-floating hydrocarbons such as oil and fuel. A vortex separator is designed to remove settleable solids and sediment-bound pollutants from surface water. On many sites, both are used together at different stages of the treatment train, depending on the pollutant risk. How is a Stormshark vortex separator installed? Units are installed below ground as an inline chamber within the surface water drainage run, connecting directly to the site's pipework. Installation depth, chamber size, and inlet/outlet configuration depend on pipe diameter, flow rate, and site levels, so it's worth sharing your drainage drawings with our team so we can confirm the right size and specification. Do vortex separators need maintenance? Yes. Because sediment collects in the base of the chamber over time, periodic desilting and inspection is required to keep the separator working effectively. Maintenance frequency depends on catchment size, surface type, and rainfall, and is typically set out in the site's maintenance plan. How much does a Stormshark vortex separator cost? Pricing depends on chamber size, pipework diameter, and site-specific requirements, so all units are quoted on application (POA). Get in touch with our team with your drainage drawings or flow requirements for an accurate price. Can Cotterill Civils help me size the right vortex separator for my site? Yes. Our team can review your drainage strategy or site drawings and recommend the correct Stormshark size for your project as part of our free drawing take-off service