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Check-Flex Limited

Check-Flex valves, from 18 mm to 3000 mm, are used on innovative drainage schemes across the UK. They maximise gravity flow, cutting or eliminating pumping costs, and are fully passive, so they need no external power.

Duckbill and inline designs give reliable, maintenance-free backflow prevention at any site, including exposed coastal and estuary locations. Fibre-reinforced, vulcanised construction (similar to a tyre) gives a service life of over twenty years.

G3 and G4 duckbill valves keep silt and sand out at the end of a pipe, and work as variable area nozzles in effluent diffusers and mixing systems.

G5 inline valves are a straightforward retrofit for odour and backflow problems in UK sewers. They fit the inlet or outlet pipe in a chamber, and the expanding clamp seals directly to the pipe for fast, leak-free installation.

Severn Estuary Long Sea Outfall Replacement (2025)

Critical infrastructure upgrade in an environmentally sensitive location

Ards North Long Sea Outfall (2023)

An integral part of NI Water’s £18m Ards North Wastewater Improvement Project to improve the quality of bathing waters in this scenic part of the Ards Peninsula

Arklow Long Sea Outfall (2023)

September 2022 saw the successful completion of a new kilometre outfall pipeline in Arklow, Ireland. The lack of wastewater treatment facilities in Arklow resulted in untreated wastewater being discharged directly to the Avoca River. The design and construction of a new wastewater treatment plant and long sea outfall was required to improve the water quality […]

Holloway Storm Relief Sewer (2021)

In the 1850s, London’s population was approximately two million. In 1858, predicting population growth, Sir Joseph Bazalgette constructed a combined sewerage system collecting both wastewater from homes and businesses, and rainwater run-off, to serve a population equivalent of four million. Now, with London’s population approaching nine million, the sewerage network can become overloaded during severe […]

Trusthorpe Outfall (2021)

The sea defences along the coast of Lincolnshire mainly comprise of concrete seawalls fronted by sandy beaches providing flood protection to the low-lying coastal flood plain, which extends up to 15km inland and has a recorded history of inland flooding as far back as the 13th century. The Lincolnshire Open Coast Flood Risk Management Scheme […]

Withernsea Long Sea Outfall - Part 2 (2021)

August 2020 saw the successful completion of a new 3.5km outfall pipeline comprising of onshore (2.5km) and offshore (1km) sections on the Holderness Coast in Withernsea, East Riding of Yorkshire. Due to continued coastal erosion, the purpose of the project was to relocate the existing Withernsea WwTW further inland and replace the exposed existing long […]

Morecambe WwTW Catchment Strategy: Part 3 (2020)

Operated by United Utilities, the Morecambe sewerage system collects at Schola Green Wastewater Pumping Station (WwPS) located in the west end of the town. From there, flows for treatment are pumped via a 6km long pipeline to Morecambe Wastewater Treatment Works (WwTW), which is situated to the south, near to the village of Middleton. Both […]

Withernsea Long Sea Outfall - Part 1 (2020)

Withernsea is located in Yorkshire, approximately 18 miles east of Hull on the Holderness Coast. The area is vulnerable to coastal erosion due to the geology being mainly soft boulder clay. Groynes and sea walls being installed in Bridlington and Hornsea have affected the longshore drift, which has caused Withernsea area beaches to narrow, providing […]

Anchorsholme Long Sea Outfall (2019)

Anchorsholme Park is located on the coast 4 miles north of Blackpool Tower. The long sea outfall (LSO) project is the third of three phases contributing to improving bathing waters on the Fylde Coast. The objective of the overall scheme is to complete the AMP6 obligations on the Fylde Coast of the ‘moving towards three […]

Bacton Combined Outfall (2019)

The North Norfolk coastline has undergone progressive coastal erosion at around the present rate for the last 5,000 years. The cliffs are made of soft deposits, mainly sand and soft clays, which are very vulnerable to erosion. This long-term coastal change puts pressure on communities, infrastructure and business in the coastal zone. The Bacton Gas […]

Morecambe WwTW Catchment Strategy: Part 2 (2019)

United Utilities’ Morecambe sewerage system collects at Schola Green Wastewater Pumping Station (WwPS) located in the west end of the town. From there, flows for treatment are pumped via a 6km long pipeline to Morecambe Wastewater Treatment Works (WwTW), which is situated to the south, near to the village of Middleton. Both sites have sea […]

Ballycastle Wastewater Project (2018)

The picturesque coastal town of Ballycastle is located on Northern Ireland’s scenic North Antrim Coast. This popular tourist spot attracts many visitors, who come to take in the beautiful scenery, as well as passing through on their trip along the famous Wild Atlantic Way. Visitors come from all over the world to see the nearby […]

Galgorm Wastewater Pumping Station Upgrade (2018)

Galgorm Wastewater Pumping Station (WwPS) is located within a busy public car park in the centre of Galgorm village, approximately 3.5km to the west of Ballymena, Co. Antrim. The WwPS is accessed via a steep laneway off the A42, Fenaghy Road, adjacent to Galgorm roundabout. Galgorm WwPS passes forward flows to Tulllygarley Wastewater Treatment Works […]

Hayle STW - Inlet Refurbishment Works (2018)

Hayle STW is located at the end of the Hayle estuary in West Cornwall approximately 7 miles east of Penzance.The area immediately surrounding Hayle STW has a small population made up of St. Erth Village. The site itself is located within a large plot bordered to the north by the West Coast Main Line, and […]

Killingworth & Longbenton Water Management (2018)

Since 2010, the Risk Management Authorities (RMAs) for the Tyneside drainage catchment have developed and implemented an area-based prioritisation process to identify and investigate those drainage areas at greatest risk of performance failure. The Killingworth, Longbenton and Forest Hall area was one of those areas identified, something supported by the published 2010 Strategic Flood Risk […]

Minworth STW - Thermal Hydrolysis Plant (2018)

Minworth STW is Severn Trent’s largest sewage treatment works and serves a population equivalent of 1.75 million from Birmingham with full flow to treatment of 1,070Ml/d. The works treats sludge arising from a population equivalent of 2.3 million which is made up of indigenous sludge plus imported sludge from the nearby Coleshill STW and various […]

Morecambe WwTW Catchment Strategy: Part 1 (2018)

The Morecambe sewerage system collects at Schola Green Wastewater Pumping Station (WwPS) located in the west end of the town. From there, flows for treatment are pumped via a 6km long pipeline to Morecambe Wastewater Treatment Works (WwTW), which is situated to the south, near to the village of Middleton. Both sites have outfall pipelines […]

Morpeth Flood Alleviation Scheme Phase 3 (2018)

Morpeth is an historic market town in Northumberland, situated on the River Wansbeck. It has suffered extensively from flooding, experiencing 22 significant flood events since 1839. In 2008, over 1,000 properties in the town were flooded or affected by flooding. The main source of flooding has been from the River Wansbeck, with Cotting Burn, a […]

Plymouth Central STW Stormwater UV Irradiation (2018)

The European Union’s (EUs) revised Bathing Water Directive (rBWD) (2006/7/EC) came into force in March 2006 replacing Bathing Water Directive (BWD) (76/1160/EEC). The overall objective of the revised directive is the protection of public health. From November 2015, a new classification system for bathing waters (excellent, good, sufficient or poor) was introduced, with more stringent […]

Prioress Mill Raw Water Pumping Station (2018)

Prioress Mill Raw Water Pumping station (RWPS) is located in Rhadyr, near Llancayo, Monmouthshire, on the south bank of the River Usk. It abstracts at a rate of up to 318 ML/day, and is the primary supply to Llandegfedd reservoir, which then feeds Sluvad Water Treatment Works (WTW). Prioress Mill RWPS has been identified by […]

Tideway Central - Overview (2018)

Thames Tideway Tunnel is the largest water infrastructure project currently under construction in the UK and will modernise London’s major sewerage system, the backbone of which dates back to Victorian times. Although the sewers built in the mid-19th century are still in excellent structural condition, their hydraulic capacity was designed by Sir Joseph Bazalgette for […]

Whittle Dene WTW (2018)

Whittle Dene Water Treatment Works is Northumbrian Water’s fourth largest treatment works with a deployable output of 118Ml/d, supplying 228,000 properties. Located in Northumberland, 13 miles west of Newcastle, it is a strategically important works to Newcastle, Gateshead, North Tyneside, South Northumberland and Tyne Valley regions. Raw water at the site comes from adjacent reservoirs […]

Bristol Road Sewer Pumping Station (2017)

Burnham Jetty is the only ‘poor’ bathing water site in the Wessex Water region as categorised by the EU Revised Bathing Water Directive. Wessex Water has been working with the Environment Agency and committed £39 million to 12 schemes to improve this rating. Bristol Road Sewer Pumping Station (SPS) and Combined Sewer Overflow (CSO) rebuild […]

Hesketh Bank WwTW (2017)

Hesketh Bank Wastewater Treatment Works (WwTW) serves a population of approximately 5,800. The catchment of this Lancashire village is mainly residential and much of the surrounding land is dedicated to agriculture. The treatment works is on the edge of the village and is situated close to the River Douglas, near its confluence with the Ribble […]

Horsley WTW (2017)

Northumbrian Water’s Horsley WTW serves around 800,000 people in the Newcastle and Tyneside area. The original works was constructed in 1977 and last extended in 2003. It draws its supply from the nearby River Tyne at Ovingham and the Whittle Dene complex of reservoirs fed from Kielder Water. The existing works has a capacity of […]

Littlemore Sewage Pumping Station (2017)

As part of the Thames Water AMP5 programme of works, Optimise was instructed to carry out an upgrade to the terminal pump station feeding Oxford STW located in Littlemore, Oxford. The terminal pump station handles flow from a population of 200,000 and the condition of the station was of considerable concern to the Environment Agency, […]

Minworth STW - Thermal Hydrolysis Plant (2017)

Minworth STW is Severn Trent Water’s largest sewage treatment works and serves a population equivalent of 1.75 million from Birmingham with full flow to treatment of 1,070Ml/d. The works treats sludge arising from a population equivalent of 2.3 million which is made up of indigenous sludge plus imported sludge from the nearby Coleshill STW and […]

Nereda in Ireland (2017)

Nereda® is an innovative, sustainable and cost-effective biological wastewater treatment technology that purifies water using the unique features of aerobic granular biomass; purifying bacteria that create compact granules with superb settling properties. The technology was originally discovered by the Delft University of Technology in the Netherlands, and developed in a unique public-private partnership between the […]

Olympia Leisure Centre and Windsor Park Storm Sewer Project (2017)

The existing combined sewerage system in the area did not have the capacity to take the increase in flow from these two major developments; therefore a new storm sewer was required. The project has also given NI Water the opportunity to update the 1930s combined drainage system in the area by the removal of significant […]

Town Beck (Ulverston) Flood Alleviation Scheme (2017)

Centrally positioned within the South Lakeland peninsula and on the border of the Lake District National Park, Ulverston is a busy Cumbrian market town with a population of around 12,000 people. The town is arguably most famous as being the birthplace of Stan Laurel, one half of the legendary comedy duo ‘Laurel & Hardy’, to […]

Wheatcroft Long Sea Outfall (2017)

August 2016 saw the successful completion of a new 2.5 kilometre long sea outfall pipeline on the east coast of Yorkshire, South of Scarborough. The purpose of the project was to replace an existing corroded and collapsed steel outfall pipe with a new solid wall polyethylene (PE) pipeline. The installation required meticulous planning by a […]

Anchorsholme Park Storage (2016)

Anchorsholme Park is located on the coast 4 miles north of Blackpool Tower. The storage project is the first of two phases contributing to improving bathing waters on the Fylde coast. The objective of the initial phase is to complete the AMP5 obligations on the Fylde Coast of the “moving towards three spills per bathing […]

Belle Greve Wastewater Centre Phase IV (2016)

Belle Greve Outfalls Replacement is the fifth and final phase of the Belle Greve Wastewater Centre (BGWwC) strategy to provide suitable wastewater treatment and disposal capability for the island of Guernsey. The strategy commenced in 2007 and was completed in 2015 with the replacement of the long sea outfall (LSO) and short sea outfall (SSO). […]

Camels Head WwTW (2016)

South West Water’s Camels Head WwTW, is located in a residential area of Plymouth, Devon and serves a population equivalent (PE) of 41,500. Capital maintenance is required due to issues with current full flow to treatment (FFT) compliance, which is constrained by the primary settlement tanks (PSTs) capacity, odour from the site, inlet screening and […]

Leeds Flood Alleviation Scheme (2016)

Historically, Leeds has not benefited from formal flood defences and is sited in a catchment where the river can rise rapidly in response to rainfall. There are records of flooding dating from the 19th century and in the recent past; prior to the scheme commencing the river had come close to flooding Leeds city centre […]

Oswestry WTW (2016)

United Utilities’ Oswestry WTW is located near to the market town of Oswestry, Shropshire on the England/Wales border. The original works became operational in 1892, near the end of the Victorian era, in response to the growing need for wholesome clean drinking water to Liverpool. It is a large works which treats raw water from […]

Shieldhall Tunnel (2016)

Construction of the Shieldhall Tunnel, the biggest investment in the Glasgow wastewater network since Victorian times, is well underway. Once complete, it will improve river water quality and the natural environment of the River Clyde and its tributaries, enable the Greater Glasgow area to grow and develop, alleviate sewer flooding key locations and deal with […]

Tideway East - Challenges (2016)

London’s sewerage system was designed by Sir Joseph Bazalgette in the 1850s, for a population of four million people. While the Victorian sewers are still in excellent working condition, they are struggling to cope with the demands of the city’s growth. Every year, tens of millions of tonnes of raw sewage pour into the River […]

What we do:

Networks - Sewerage: Outfalls | Pipelines - Sewers | Valves