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Flapvalves – NRV’s

Flapvalves – simple yet effective protection

  • Quick and Easy to install
  • Lightweight yet robust
  • Low head losses
  • Virtually maintenance free
  • Various mounting arrangements
  • Fish friendly solutions available


ACE KRK Flap valves are available in a wide range of models, chosen to suit our customer’s individual needs. They are manufactured in HDPE and Stainless Steel 316L, making them lightweight for ease of handling and installation, without compromising strength. HDPE is very shock absorbent, and does not crack if struck, making it ideal for this type of equipment.

KRK Flap valves are either bolted to a wall using resin anchors, or pipe mounted using a number of quick and easy methods depending on applications, all of which do not usually require grouting – typically KRK flap valves take a matter of hours to fit, with minimal setting-dry and no curing time. The benefits to cost and time saving are clear when compared with more traditional types.


Using self lubricating hinges, the ACE KRK Flapvalve only requires occasional visual inspection to check for obstruction, and no greasing is required. The EPDM seal also allows for some wear, offering reliable protection throughout the lifetime of the product.

Although HDPE is lightweight yet robust, it is also partially buoyant in water, so when the KRK flapvalve is fitted with it’s counterweight, it is perfectly balanced; the upstream head required to open it is minimal, but full closure is ensured as soon as it’s needed.


Flexible options


As some outfalls require reliable protection from flooding, but in doing so create a barrier to fish migration, ACE offer a number of fish friendly flap valves, and are more than happy to discuss your requirements to provide a suitable solution- please contact us for more details.

If fitted to a pumped outfall, or to a sea outfall, more heavy duty flap valves are also available, so please contact ACE if you have requirement in a more aggressive environment, and we will be happy to help.



Although ACE stock a wide variety of sizes of KRK flapvalve for quick dispatch (100-800mm), our flapvalves can be customised to suit specific requirements, either to adhere to particular specifications, or to save complicated construction, or modification to existing structures.

Since introduction of the HDPE KRK Flap valve range, the material has become synonymous with high quality, reliable flood defences, offering extremely good value for money over it’s life- it’s not just any “plastic” valve!



For more information on our previous flap valve projects, please see our case studies.

Wall mounted flapvalves
Pipe mounted flapvalves
Flange mounted flapvalves
Angled flapvalves
Pumped flapvalves
Fish friendly flapvalves

Mounting Options

ACE supply a variety of standard mounting arrangements on KRK flap valves, to save installation time, such as:

  • KRK-R-O Flapvalves – Face Wall mounted, circular (or square, KRK-V-O)
  • KRK-R-P Flapvalves – for mounting directly to Plastic pipe with couplings
  • KRK-R-BS Flapvalves – for mounting directly into pipe, using a push-fit spigot
  • KRK-R-F Flapvalves – for mounting to pipe flanges
  • KRK-R-OH Flapvalves – wall mounted, but hung on a backward angle (prevents wave action)
  • KPK Flapvalves – Suitable for pumping or aggressive environments, fitted using either F or OH connections.
  • Fish friendly flapvalves

Our equipment is very easy to install – please see below or click https://youtu.be/mis51OqTChQ to see a short video overview. Alternatively, please see our documents section for installation instructions.

In some instances, an inline application is required, or space, wave action or other conditions prevent the use of flap valves. Please see our Wastop range for an alternative to flap valves.

As with all ACE equipment, we have a wide range of standard flap valve designs for quick dispatch, however we pride ourselves on our ability to customise designs to specific requirements, or to use our wealth of experience to provide a fully tailored, value engineered solution. Please see our case studies and design pages for more details of our capabilities. Alternatively, please contact us for more details.

Installation video



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