{"product_id":"high-capacity-anti-vortex-roof-drain-outlet","title":"High-Capacity Anti-Vortex Roof Drain Outlet — Aluminium Vertical Spigot, 50-160mm","description":"\u003cp\u003eMost flat roof outlets are sized for a domestic patio or a garage — a 50mm or 75mm bore, rated for the rainfall a small roof will ever see. Scale that same outlet up to a large commercial deck, and the maths stops working: the outlet becomes the bottleneck, not the roof. In a heavy downpour, water backs up faster than it can leave, ponds against the upstands, and in the worst case overflows the parapet before the standard outlet has cleared it.\u003c\/p\u003e\n\n\u003cp\u003eThis is a large-capacity, anti-vortex gravity outlet built specifically for that problem. It uses a baffled dome or flat grate to break up the swirling vortex that normally chokes a plain outlet's flow, so the pipe underneath can run far closer to its true full-bore capacity. It is still a straightforward gravity outlet — no pumps, no siphonic priming, nothing bespoke to specify — just a better-engineered casting that clears more water per minute through the same size of pipe.\u003c\/p\u003e\n\n\u003ch3\u003eSpecification\u003c\/h3\u003e\n\u003ctable style=\"border-collapse:collapse;width:100%;max-width:640px;\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:left;padding:8px;border:1px solid #ddd;background:#f5f5f5;\"\u003eSpec\u003c\/th\u003e\n\u003cth style=\"text-align:left;padding:8px;border:1px solid #ddd;background:#f5f5f5;\"\u003eDetail\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eDiameters\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003e50mm, 75mm, 110mm, 160mm vertical spigot\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eMaterial\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eAluminium casting, mill finish\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eGrate options\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eDome grate (general use) or flat grate (trafficked\/paved areas)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eFlow performance\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eAnti-vortex baffle design drains up to 40% more roof area than a standard gravity outlet of the same bore, per published manufacturer flow-capacity data\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eFitting type\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eVertical spigot outlet, bonds into single-ply, mastic asphalt or built-up felt roof build-ups\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eSuitable decks\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eConcrete, timber and metal flat roof decks\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eTypical use\u003c\/td\u003e\n\u003ctd style=\"padding:8px;border:1px solid #ddd;\"\u003eLarge commercial and industrial flat roofs, car park decks, podiums, warehouse roofs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eWhy choose an anti-vortex outlet over a standard gravity outlet\u003c\/h3\u003e\n\u003cp\u003eA plain gravity outlet lets water spin as it drops into the pipe. That swirl drags air down with it, which cuts the effective flow because the pipe is running part-full of air rather than water. The baffle inside an anti-vortex grate breaks that spin before it starts, so the outlet can push a genuinely higher volume of water down the same diameter of pipe in the same downpour. For a roof designer or contractor, that means fewer outlets are needed to hit the same drainage design flow — or the same outlet count copes safely with a larger catchment area and a more severe storm event.\u003c\/p\u003e\n\n\u003ch3\u003eFrequently asked questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIs this a syphonic drainage system?\u003c\/strong\u003e\u003cbr\u003eNo. This is a gravity outlet with an anti-vortex baffle, not a syphonic (engineered, primed) system. Syphonic drainage is a bespoke, project-specific design with no standard off-the-shelf price. This outlet is a standard stocked product that installs the same way as any gravity roof outlet — no design calculation, priming or specialist commissioning required.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat's the difference between the dome grate and the flat grate?\u003c\/strong\u003e\u003cbr\u003eThe dome grate sits proud of the roof surface and is the standard choice for most flat roofs — it has more strainer area exposed, so it copes better with leaves and debris. The flat grate sits level with the surrounding surface and is intended for outlets on a trafficked or paved area (a roof terrace or car park deck) where a raised dome would be a trip hazard or get damaged by vehicles.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow many of these does my roof need?\u003c\/strong\u003e\u003cbr\u003eThat depends on your roof area, local rainfall intensity and pipe run design, which is a job for your roofing contractor or drainage designer working to BS EN 12056-3. As a guide, each outlet here will generally cope with a larger catchment area than an equivalent-diameter standard domestic outlet, but we can't give a safe outlet count without your roof's dimensions and drainage design — call our technical team if you'd like help working through it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan this replace a blocked or undersized outlet on an existing roof?\u003c\/strong\u003e\u003cbr\u003eYes, on a refurbishment the existing outlet can usually be cut out and this unit bonded into the membrane in its place, provided the pipework below is the same bore or can be adapted. On a re-roof this is exactly the point at which to upsize, since the outlet is far cheaper to change now than once the new membrane is down.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it come with a leaf guard?\u003c\/strong\u003e\u003cbr\u003eThe dome grate itself acts as a coarse strainer against leaves and debris. For roofs near trees we'd still recommend a routine gutter-and-outlet clearance as part of annual roof maintenance — no outlet, however well designed, stays clear indefinitely without one.\u003c\/p\u003e\n\n\u003ch3\u003eInstallation \u0026amp; ordering guidance\u003c\/h3\u003e\n\u003cp\u003eSelect the diameter to match your downpipe or drainage run, and the grate type to match how the roof area around the outlet will be used. The outlet bonds into the waterproofing membrane in the same way as a standard gravity outlet: cut the membrane to the collar, lap it over the outlet flange, and bond with contact adhesive and uncured flashing tape for a fully watertight joint, positioned at the lowest point of the roof. Because pricing and lead time step up meaningfully with diameter, it's worth confirming your required bore with your drainage design or downpipe size before ordering — our technical team is on hand if you're not sure. Call 02031510153 or email sales@rubberroofuk.uk.\u003c\/p\u003e\n\n\u003cp\u003eIf your roof only needs a small, domestic-scale outlet rather than this large-capacity range, see our \u003ca href=\"\/products\/epdm-roof-drain-outlet-with-leaf-grate-rubber-roof-uk\"\u003eEPDM Roof Drain Outlet with Leaf Grate\u003c\/a\u003e. If you need a threaded (screw-fit) connection rather than a spigot, see our \u003ca href=\"\/products\/aluminium-vertical-threaded-roof-drain-outlet-dome-grate\"\u003eAluminium Vertical Threaded Roof Drain Outlet\u003c\/a\u003e.\u003c\/p\u003e","brand":"Rubber Roof UK","offers":[{"title":"50mm \/ Dome Grate","offer_id":46130490409151,"sku":"RRUK-AVOUT-50-DOME","price":394.99,"currency_code":"GBP","in_stock":true},{"title":"50mm \/ Flat Grate","offer_id":46130490441919,"sku":"RRUK-AVOUT-50-FLAT","price":514.99,"currency_code":"GBP","in_stock":true},{"title":"75mm \/ Dome Grate","offer_id":46130490474687,"sku":"RRUK-AVOUT-75-DOME","price":659.99,"currency_code":"GBP","in_stock":true},{"title":"75mm \/ Flat Grate","offer_id":46130490507455,"sku":"RRUK-AVOUT-75-FLAT","price":684.99,"currency_code":"GBP","in_stock":true},{"title":"110mm \/ Dome Grate","offer_id":46130490540223,"sku":"RRUK-AVOUT-110-DOME","price":859.99,"currency_code":"GBP","in_stock":true},{"title":"110mm \/ Flat Grate","offer_id":46130490572991,"sku":"RRUK-AVOUT-110-FLAT","price":959.99,"currency_code":"GBP","in_stock":true},{"title":"160mm \/ Dome Grate","offer_id":46130490605759,"sku":"RRUK-AVOUT-160-DOME","price":1124.99,"currency_code":"GBP","in_stock":true},{"title":"160mm \/ Flat Grate","offer_id":46130490638527,"sku":"RRUK-AVOUT-160-FLAT","price":1189.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0598\/1804\/9727\/files\/high-capacity-anti-vortex-roof-drain-outlet-installed-flat-roof.jpg?v=1788338133","url":"https:\/\/rubberroofuk.uk\/products\/high-capacity-anti-vortex-roof-drain-outlet","provider":"Rubber Roof UK","version":"1.0","type":"link"}