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Drainage & Piped Services Standard Specification
Version 2014-1

Integral accessories: Submit proposals.

Execution

Installing precast concrete access chambers and shafts for below ground drainage type C
Standards: To BS EN 752, and in accordance with relevant parts of the National Annex (NA); In accordance
with relevant parts of Sewers for adoption; In accordance with relevant parts of Sewers for Adoption,
Northern Ireland; and In accordance with relevant parts of Sewers for Scotland.
Base slab thickness: 225 mm.
Chamber dimensions:

Size (nominal internal): Submit proposals.
Depth (cover level to pipeline invert): As manhole schedule.
Concrete surround: 150 mm thick.
Backfilling:
Laying fill: Submit proposals.
Compaction: By hand in 100 mm layers.

Fixing steps in below ground drainage monitoring and control systems type F
Fixing: Secure to chamber wall.
Positioning: 300 mm vertical centres staggered 300 mm horizontally, with lowest step 300 mm (maximum)
above benching and top step 450 mm (maximum) below top of cover.

Jointing precast concrete below ground drainage access chamber sections type D
Inner joint surface: Trim surplus jointing material extruded into chamber and point neatly.

Laying conventional channels, branches and benching in access chambers for below ground drainage type
C
Main channel: Bed solid in 1:3 cement: sand mortar.
Branches:

General: Connect to channel, preferably at half pipe level, so that discharge flows smoothly
in direction of main flow.
Branches greater than nominal size 150 mm: Connect the branch soffit level with the main
drain soffit.
Connecting angles more than 45° to direction of flow: Use three-quarter section channel
bends.
Benching:
Profile: Rise vertically from top of main channel to a level not lower than soffit of outlet pipe,
then slope upwards at 10% to walls.
Topping: Monolithic with benching, and with dense smooth uniform finish.
Application: Before benching concrete has set.

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