After an extensive research programme, Marshalls CPM introduced the 1200 Perfect Manhole system in October 2009 to meet the challenges of modern day construction. Today, it is available in 1200mm, 1500mm and 1800mm diameters and comprises of a monolithic precast concrete base (available pre-benched in any configuration within just days of requisition), a sealed chamber ring (with a thicker wall than a standard ring), a rubber joint (so no tokstrip of similar product is required) and a sealed cover slab which is supplied with your required access.

This unique system of products combines to form the Marshalls CPM Perfect Manhole system; designed and manufactured to last a minimum of 120 years that provides a sealed manhole system that gives up to 40% savings on greenhouse gases compared to traditional manhole construction and eliminates 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, making safe site practice a real winner when using the Perfect Manhole as it reduces 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.

The Perfect Manhole complies with BSEN 1917:2002 and BS5911-3 and has been accepted for use by all major UK companies.

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Advantages of the 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.
  • No need to surround in concrete unless specifically required – 130mm wall thickness.
  • Available at short notice – Our modern methods of production enables just in time delivery of all components including monolithic bases at short notice.
  • Design freedom – All designed monolithic perfect base characteristics such as location of the inlets and outlets and invert configuration can be manufactured individually and exactly in accordance to the wishes of the specifier and client.
  • Perfect Hydraulics – everything flows. Optimised flow characteristics by customised base configuration of all inlets and precise drop in channels and pipe connections.
  • 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*
  • Combined seal includes load distributor – Load distribution ensures even distribution of vertical loads*.
  • Allows joint inspection – Correct installation can be visually confirmed.
  • Efficient construction – Available in varying depths for efficient construction
  • Base options – available pre-benched or plain bottom with or without inlet/outlets.
  • Pre-fit options – Hydro-brakes, penstocks, non-return valves and filters can be pre-fitted at the factory
  • 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.
  • Full take-off service available
  • Lifting apparatus available for fast, effective and safe handling

*Please note 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.

If you would like a CPD style presentation on the Marshalls CPM Perfect Manhole system please call our marketing team on 01902 356220 or email

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1200mm Perfect Manhole dimensions


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1500mm Perfect Manhole dimensions


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  • Do you supply certificates of conformity for your standard products?

    No – they are not required as our standard products are certified under the BS ‘Kitemark’ system – certification can be viewed here.

  • How frequent should I be testing the pipeline during installation?

    It is highly recommended to test the pipeline every 3 or 4 pipes laid as an absolute minimum (do not wait until whole line is installed before carrying out such test).

  • What is the standard position of the access opening in cover slabs?

    The standard access position is 150mm in from the chamber wall below (measured from centre of nearest access edge to inside of chamber wall below). Other positions/access sizes/multiple access slabs can be made to order.

  • Where can I get additional assistance on the use of concrete drainage products?

    Additional assistance can be had via the Concrete Pipeline Systems Association, see

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