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Concrete Manhole Cover Slab.
  • Concrete Manhole Cover Slab.

1200mm Sealed Concrete Manhole Cover Slab



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Product Details

This item is supplied to order and additional refund & returns terms apply.


Product Type: Sealed Concrete Cover Slab
Model Type: Eccentric Access Opening
Chamber DN: 1200mm
Overall DN: 1460mm
Manhole Access Sizes: 600x600mm & 675x675mm
Approx Weights: 615kg & 600kg

This reinforced concrete sealed cover slab is designed to form part of CPM's Perfect Manhole System. Used as a cap for sealed manhole chamber rings that have a 1200mm nominal diameter, the rubber seal between the two works to create a watertight seal without the need for an additional concrete surround.

It is available with either a 600x600mm or 675x675mm square eccentric access opening.

Product Features at a Glance:

  • 600mm & 675mm square openings available
  • Eccentric access positioning
  • Quick and easy to install
  • Watertight on construction
  • Safe lifting system
  • Cost saving
  • No concrete jacket required

Concrete cover slabs, also referred to as “biscuits", reducing slabs and lids, are used to complete the main shaft construction of a manhole chamber. Sitting on top of the chamber rings, they create a single access opening for maintenance purposes. As well as acting as a platform to cap the manhole chamber, they also provide a base for any regulating brickwork or seating/adjusting units prior to finishing with the manhole lid.

The CPM Perfect Manhole System is comprised of a monolithic precast concrete base, a sealed chamber ring, a rubber joint (so no tokstrip or similar product is required) and a sealed cover slab. This unique range of products are designed and manufactured to last a minimum of 120 years and give up to 40% savings on greenhouse gases compared to traditional manhole construction. They eliminate the need of ready mixed concrete to form the traditional base, chamber benching and further concrete to surround the manhole.

A complete manhole can be installed in as little as 30 minutes, helps ensure safe site practice by reducing the need to work in confined spaces and eliminates the need for wet trades resulting in rapid construction compared to traditional methods as well as a reduction in the time the excavation is open. 

Key Features of the CPM Perfect Manhole System: 

  • Safer construction – No requirement to work in confined spaces. No requirement to form a concrete surround. Reduction of open excavation. 
  • GHG Savings – Up to 40% savings on GHG emissions compared with traditional build. 
  • Fast installation – The modular solution eliminates the need for wet trades resulting in rapid construction compared to conventional methods. 
  • Thicker Walls – No need to surround in concrete unless specifically required.
  • Watertight – The combination of a thicker wall and rubber joints ensures a watertight structure. 
  • No water ingress into sewerage network reduces treatment costs – The combination of a 130mm wall and sealed rubber joint to withstand a minimum of 5m / head pressure*.
  • No ex-filtration – the seal prevents raw sewage or dirty water from escaping into the surrounding area.
  • Combined seal includes load distributor – Load distribution ensures even distribution of vertical loads**.
  • Allows joint inspection – Correct installation can be visually confirmed. 
  • Base options – available pre-benched or plain bottom with or without inlet/outlets. 
  • Flexible connections – The perfect manhole can connect to plastic, clay or concrete giving you a larger choice. 
  • Fully tested under factory conditions – The whole system from base to cover slab is subject to testing. 
  • Kitemarked solution manufactured under factory conditions – Complies with the requirements of BSEN 1917 and BS5911-3. 
  • Concrete for Life – Built to last. High quality durable concrete with a minimum 120 year design life. 
  • Customer choice The perfect manhole is available with or without double steps. Sealed chamber rings can be used without the perfect base. 
  • Marshalls CPM Perfect Manhole is accepted for use by all major UK companies and is included in Sewers for Adoption.

*Watertightness is defined in BS EN 1917 as resisting a 5m head for 15 minutes, this is to simulate a temporary surcharge condition not a permanent head of water. 

**Shafts in high water tables are subject to buoyancy effects. For further information please contact our technical team. 


Please Note: All dimensions and weights are approximate as concrete product dimensions can have slight variations due to their manufacturing process. Customers should ensure that lifting equipment has sufficient capacity to allow for variations. All images shown are used for illustration purposes only and may differ from the actual product supplied.  

16-20 working days
Product Type:
Manhole Cover Slab
Install Type:
Eccentric Opening
Marshalls CPM
Nominal Size: