How deep do I need to dig?

Each individual local authority has their own adopted rules for depth of chambers. The depth required is usually expressed as “depth of cover”, which is the measurement from the top of the ducting to the surface/ground level. NJUG (National joint utilities grouping which was set up by the government of the day to set a universal standard for this sort of issue recommended the following:

If the ducting is to be installed under a footpath then there should be a minimum depth of cover of 450mm.

If the ducting is to be installed under a carriageway then there should be a minimum 750mm depth of cover. Where the ducting runs under a carriageway this does not mean that the chambers are suitable to be installed in a carriageway. The chambers shall be installed in the footway adjacent to the carriageway at a sufficient depth to ensure a 750mm depth of cover for the ducting.

Ids chambers have been designed to meet these requirements. Two chambers deep will give 463mm depth of cover using 110mm O.D. ducting. Three chambers deep will give a 793mm depth of cover using 110mm O.D ducting,

As stated previously these are only recommendations and as such each unitary authority is free to impose their own guidelines. Some authorities insist on a 600mm depth of cover in the footway so to accomodate this Ids have produced a raising piece. The raising piece differs from the chamber in that it is only 250mm deep which because of the way that the chambers interlock will provide an extra 200mm depth of cover. Therefore two chambers plus a raising piece will provide a 663mm depth of cover over a 110mm duct. (463mm (chambers) + 200mm (raising piece)=663mm).

IMPORTANT
Only one raising piece can be used on each pit therefore the number of raising pieces must never exceed the quantity of covers required.

What duct can I use?

IDS can be used to aid the installation of 63mm, 107mm, 110mm and 168mm overall diameter duct.

What chamber clear opening sizes are available?

The moulded plastic chambers are available in 300mm2, 300 x 450mm, 450mm2, 450 x 600mm and 600mm2. For use with traffic signals there are 2 sizes a 300 and 450mm diameter.

What covers and frames do I use?

The IDS moulded plastic chamber range is complemented by a range of B125 composite covers and ductile iron frames. Also available is our new range of B125 and C250 ductile iron covers and frames all manufactured to suit the chamber clear openings.

Do I need a concrete surround?

We recommend a concrete surround for our pre-moulded plastic drawpits. Although our new range of IDS mark 2 can be installed without the need for concrete surround by using a well compacted 10mm aggregate surround. We are also able to offer a soil stabliser. Soil Stabiliser is mixed with the spoil as it is excavated therefore reducing soil off site. For more information about this product contact us.