Flap Valve Installation

Flap valves are important to prevent reverse flow of water into holding structures, protecting water assets from contamination, animal ingress and flooding. The Drinking Water Inspectorate (DWI) recommends that flap valves should be installed on all drainage and overflow routes and inspected every six months.

Stonbury is pleased to assist its clients in the inspection, installation and maintenance of flap valves and their associated outfall structures, deploying teams which are specially trained to work in confined spaces and riverine and tidal environments.

Identification and inspection

Outfall pipework is often situated in difficult-to-access locations and is frequently obscured by silt and vegetation. Stonbury is pleased to assist clients to carry out investigatory works to identify the locations of pipework and existing valves, along with the following services:

• Supplying safe temporary access
• Dewatering and isolation of outfall locations
• Vegetation clearance including weeds, scrub, and trees.
• Silt, mud, and debris build-up removal
• Clearance and inspection of pipework to ensure free-flowing drainage routes
• Camera surveys

Stonbury takes preservation of the environment seriously and has teams that are trained in the protection of sensitive habitats such as nesting wildfowl and are educated in rare and invasive plant species.

Installation, repair, and maintenance

Once accessible, Stonbury provides the following services, installing flap valves in a range of sizes and materials to suit the environment and client specification.

• Replacement of missing or damaged valves
• Removal and replacement of existing cast iron flap valves for new, lighter, more sustainable designs – types include Ductile Iron and High-Density Polyethylene (HDPE)
• Installation of alternative design valves such as push-fit and duck-bill valves
• Bespoke fabrication
• Design and build of headwalls and chambers
• Fitting of pull chains to existing valves
• Excavation of outfall ditches
• Concrete, brick, and stone works to widen chambers
• Freeing and repair and refurbishment of existing flap valves
• Crane lifting of large flap valves in challenging locations

Permanent access

In addition to the above services, Stonbury improves or installs access to allow regular valve functionality inspections. Examples include:

• Stepped access
• Concrete and steel walkways
• Handrailing
• Ladders