CD 534: Chamber Tops and Gully Tops for Road Drainage and Services, now at version 0.2.0. is here Find out more
Retrofittable seal plates
DropSeal
Our retrofittable seal plates provide a simple and effective way to reduce the ingress of surface water, debris and contaminants into underground chambers and sewer networks.
Designed to fit compatible manhole cover systems, they can be installed, removed or upgraded without replacing the existing cover and frame, giving asset owners greater flexibility as network requirements evolve.
DropSeal seal plates are retrofit, ductile-iron plates that can provide three levels of sealing for manhole covers after installation. Installed beneath the existing cover by simply dropping into place, the seal plate creates a barrier that helps reduce the passage of odours and surface water through the chamber top.
Ideal for drainage and sewer applications, DropSeal can be fitted to compatible manhole covers without removing or replacing the original frame, making it a simple and cost-effective upgrade for existing installations.
A practical retrofit solution
Sealing requirements can change over time due to environmental conditions, changing site use, or network performance issues. DropSeal provides a straightforward way to enhance the sealing performance of installed ironwork without the cost, disruption, and reinstatement associated with replacing the entire cover and frame.
By fitting beneath the existing cover, the seal plate helps create a more controlled interface between the chamber and the surface environment while maintaining access when required.
Available with Three leak-tightness levels
Different locations within a sewer network face different levels of risk. DropSeal offers three selectable leak-tightness levels aligned with recognised Water Industry Specification classes. This allows operators to apply the appropriate level of sealing where it is required.
Three selectable leak-tightness levels
As defined by the Water Industry Specification (WIS) classes
Direct-fit seal plate - no bolted trays or secondary frames
Resulting in quicker more efficient installations
Full clear opening maintained for safe access
Reducing risk during entry and avoiding restricted or non-compliant openings
Retrofittable installation once the frame is in place
Allowing the plate to be moved to where its needed, when its needed
Surface water entering foul-only sewer networks can create significant operational challenges.
Under shallow ponding conditions, water can pass through the tolerances of standard manhole covers and enter the sewer system. Independent Water Industry Specification testing has demonstrated that a single 600 x 600 cover can admit flows equivalent to the peak foul load from hundreds of properties.
That water is then pumped, treated, and managed as wastewater, placing unnecessary demand on pumping stations and treatment infrastructure.
DropSeal provides a practical way to reduce that infiltration at the source.
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Climate change and increasing rainfall pressures
More frequent and intense rainfall events are placing increasing pressure on foul sewer networks, particularly in densely developed urban areas where network capacity is already limited.
During heavy rainfall, surface water can enter foul-only systems through standard manhole covers, increasing flows within the network and placing additional demand on pumping stations and treatment infrastructure.
WIS 4-26-01 highlights the significance of this inflow, with testing demonstrating that a standard 600 x 600 mm cover can admit substantial volumes of water under relatively shallow ponding conditions.
In many cases, smaller foul-only pumping stations operate at around 11 litres per second capacity. This means that inflow through submerged covers alone can be enough to overwhelm local infrastructure, increasing the risk of surcharge, overflow events and unnecessary treatment of clean water.
DropSeal helps limit surface water entering foul networks at the source.
By introducing a selectable sealing solution within compatible Highway and Unite manhole cover frames, the DropSeal supports a more targeted approach to infiltration control, helping operators reduce unnecessary stormwater entering foul-only systems during periods of heavy rainfall.
The Sea Starts Here
What enters our drainage networks does not simply disappear. Managing storm water responsibly at source is an important part of reducing pressure on wastewater systems and helping protect rivers, coastlines and the wider environment.
We hope our ‘The Sea Starts Here’ campaign will go some way to increasing the awareness to a wider audience about, the interconnectedness of our infrastructure and the problems of water pollution and its effect on marine wildlife. These are important issues to us and our industry and we hope the message will resonate with people to help create lasting change.
UK water industry standards recognise the importance of controlling infiltration and protecting network capacity. DropSeal provides a practical, flexible way to reduce surface water entering underground assets while maintaining safe and unrestricted access.
Unlike permanent sealing systems, DropSeal uses a direct-fit ductile iron seal plate that can be installed, upgraded or removed as operational priorities change. Once a compatible frame is in place, sealing becomes an option that can evolve alongside the network rather than being fixed at the point of installation.
Available in multiple leak-tightness classifications aligned with Water Industry Specification (WIS) requirements, DropSeal allows asset owners to apply the right level of protection where it's needed today, while retaining the flexibility to adapt tomorrow.
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Why are low-leak manhole covers so important?
Low-leak manhole covers allow water to percolate in slowly and in a controlled manner, rather than all at once, which allows sewer systems to handle the smaller additional volume. Low-leak covers are currently specified rather than fully sealed ones, but the latter prevent water from entering and contribute to surface flooding.
This lack of drainage also results in ‘ponding’ around the cover, which is a traffic hazard and accelerates the corrosion of the manhole covers. It can also be a cause of potholes forming in and around the manhole cover.
Built for installation and operation
DropSeal has been designed with both installers and operational teams in mind.
The seal plate mirrors the cover’s BS 7903 lifting key points, allowing operatives to use the same lifting methods and equipment they already trust. The indexed design ensures the seal plate can only be installed in the correct orientation.
Operational advantages include:
Indexed installation for correct positioning every time
Seal plate mirrors standard lifting points
No specialist tools required
Full chamber access maintained
This helps ensure sealing solutions remain practical to use throughout the asset’s service life.
