Underground Manhole Chamber Riser

The Underground Manhole Chamber Riser is designed to increase the height of compatible inspection chambers so the finished cover level matches surrounding ground levels. It is commonly used during new drainage installations or when existing chambers need raising after driveways, patios, paving or landscaping works.

Manufactured from polypropylene, these risers offer a lightweight, non-rusting alternative to concrete components and are easier to handle on site. Each riser is supplied with a joint seal to help create a secure connection with the matching chamber base.

Two size options are available. The 320mm diameter riser provides a 400mm rise and is suited to smaller domestic chamber systems. The 450mm diameter riser provides a 300mm rise and is commonly used on larger inspection chambers and higher duty installations.

These risers are made from recycled material and are compliant to relevant clauses of BS EN13598-1:2010 and Sewers for Adoption, 7th Edition when installed correctly with compatible components. The 320mm model is compatible with matching CD U351 or CD U353 chamber bases. The 450mm model is designed for use with the matching CD U453 chamber base.

Always select the correct chamber size before ordering. Check existing chamber diameter, required finished height and compatible cover loading before installation.

Underground chamber riser for raising inspection chamber height

Available in 320mm and 450mm diameter options

Lightweight polypropylene construction

Non-rusting design for underground use

Supplied with joint seal

Ideal for driveway, patio and landscaping level changes

Manufactured from polypropylene with EPDM rubber joint seal. Polypropylene provides a durable non-corrosive chamber component, while the seal helps create a secure connection between chamber sections.

Product type: Underground chamber riser
Material: Polypropylene (Grade AP9)
Seal material: EPDM rubber
Colour: Black
Supplied with joint seal

320mm Diameter Option (CD U355)
Clear opening: 320 mm
Overall height: 440 mm
Rise height: 400 mm
Approx. weight: 2.6 kg
Load rating: 35 kN (3.5 tonnes) when correctly installed
Compatible bases: CD U351 / CD U353

450mm Diameter Option (CD U455)
Clear opening: 450 mm
External diameter: 500 mm
Overall height: 340 mm
Rise height: 300 mm
Approx. weight: 3.5 kg
Load rating: Up to B125 (12.5 tonnes) when correctly installed
Compatible base: CD U453