Internal Underslab Manholes

Product Overview

Built offsite, our range of Pipex thermoplastic Underslab Manholes are available in rectangular or circular finish with branch inlets configured to suit project specific drainage layouts.

The manholes are factory manufactured to BSEN13598-2 as stated in Sewers for Adoption 7th Edition, and every manhole is factory tested prior to site delivery.

Various options are available such as factory installed rebar reinforcement to interface with concrete raft slab designs, shuttering, internal bolted hatch box and top formwork to interface with the structural floor slab.

Top Formworks are provided to interface project specific manhole covers and frames.

Materials of Manufacture

  • Polypropylene (PPH)
  • High Density Polyethylene (HDPE)


  • Smooth Internal bores prevent the build-up of FOG’s (fats, oils and greases), suitable for pressure jetting to WRc standard and sealed against odours
  • BBA approved to 3-metre diameter x 6-metre depth to BS EN 13598
  • Bespoke and standard sizes factory manufactured offsite, for fast track installation
  • 60+ years design life as stated in the BBA Certificate
  • Adjustable turret and watertight seal available for perfect interface with structural slabs
  • Highly corrosion resistant
  • Suitable for mass poured concrete slabs and suspended drainage system
  • Lightweight properties enabling fast track site installation
  • Thermoplastic benching and channels improve hydraulic performance ref: BSEN752 NA.
  • Branch inlets connections suitable for all types of drainage pipework systems such as cast iron, vitrified clay and twin wall HDPE pipework

Watch our video now to see how our underslab manholes could enhance your projects.

Contact our technical expert for more information: [email protected]

Relevant resources

  • Flyers


  • FGS PXT Underslab Manhole Flyer
  • FGS PXT Manhole Internal Hatch Boxes
All Pipex Flow and Environmental Solutions Products

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