Building Construction Handbook, Eighth Edition

Inspection Chambers ~ these provide a means of access to drainage
systems where the depth to invert level does not exceed 1„000.

Manholes ~ these are also a means of access to the drains and
sewers, and are so called if the depth to invert level exceeds 1„000.

These means of access should be positioned in accordance with the
requirements of part H of the Building Regulations. In domestic
work inspection chambers can be of brick, precast concrete or
preformed in plastic for use with patent drainage systems. The size
of an inspection chamber depends on the depth to invert level,
drain diameter and number of branch drains to be accommodated
within the chamber. Ref. BS EN 752: Drain and sewer systems
outside buildings.

Typical Details ~

brick levelling course

one brick wall in

dense engineering

quality bricks

bedded in cm. mt.

(1:3) and laid in

English bond

branch drain

150 mm thick

mass concrete

(1:3:6) base

brick levelling course

precast concrete

cover slab

precast concrete

chamber sections

to BS 5911- 4, circular

or rectangular

shapes available

precast concrete

base unit with main

channel and branch

channel(s) cast in as

required

branch drain

step irons required for invert levels over 1„200 deep

600 × 450 light duty cover and frame

bedded in cm. mt.

600 × 450 c.i. cover and frame

600 minimum

1:6 fall

main

drainage

channel

100 mm thick

precast concrete

slab

150 mm mass

concrete

encasing

required in wet

subsoils

25 mm thick (1:1)

cement/sand

topping to 1:6

fall over mass

concrete benching

main

drainage

channel

arch or

lintel

over pipe

Simple Drainage---Inspection Chambers