This FAQ answers essential questions about cable pits, covering their purpose, design, materials, installation, safety, and maintenance. It explains how cable pits facilitate safe and efficient underground cable management across various environments, while addressing key concerns like durability, security, and compliance with standards.
Q&A:
- Why are lid or cover aesthetics important for cable pits?
Pavements visually and physical interact with the environment. If not specified thoughtfully, service enclosures will interrupt visual continuity. For more info, click here
2. What are cable pits?
These are pits positioned along underground cable routes for branching and bending of cables and to allow surface level access for jointing and maintenance through removable lids and access covers. For more info, click here
3. What are surface ducting systems?These are shallow trench runs which run along cable routes allowing access through removable lids and access covers. For more info, click here
4. How are cables managed in a cable pit?
Cables can be drawn, joined (jointed) or reorientated (direction change). For more info, click here
6. What’s in a cable pit?
Cable pits generally contain low voltage electrical cables or cables for data or communications. For more info, click here
7. Where are cable pits found?
Cable pits can be found along cable routes in domestic, urban and civil environments. For more info, click here
8. Is there an Australian Standard for cable pits?
There is no Australian Standard that applies to service pits. However AS 3996 governs access covers and lids therefore manufacturers should provide independent certified test certificates for these trafficable elements. Designers need to consider the anticipated traffic scenario over each enclosure. A single cable route can pass through a number of different environments and every service pit along cable route may be exposed to a different traffic scenario.
A lack of consideration can lead to overdesign or failure. For more info, click here
9. Can cable pits be installed in roads?
Cable pits should not be placed in areas of fast moving traffic i.e. roads AS 3996 gives approx. slow moving wheel loads
Consider the axle exerting the greatest load and divide to reduce this load to only the wheels that will make contact on the lid or cover. For more info, click here
10. What is the difference between a lid and an access cover?
Lids have a solid top and fit directly into pit structures. Access covers comprise a separate cover and frame system which is installed integrally into pavements/slabs and provide a better barrier for water ingress. Access covers make no contact with the pits structure and installed ‘above’ the pit. They are either solid top or (infill to accommodate pavement materials). Manufacturers should provide typical ‘separation’ dimensions between frame and pit.
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11. What is there to consider when selecting a lid or a cover for a cable pit?
Depending on the installation, certain user requirements are considered critical to the asset owner or maintenance crew. E.g. access frequency, protection against foreign objects. slip resistance, aesthetics, identification, security. Manufacturers should provide solutions and (where appropriate, support with documentation) to meet unique client requirements.
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12. How do you size a cable pit?
Choosing the correct enclosure size will depend on the minimum bending radius of cables (refer to cable manufacturer’s recommendations), minimum depth to cables (refer to Standards) and in some cases allowance is required for segregation of cables, future introduction of cables or storage of equipment.
Caution: Most cable pits are narrower at the base for ease of manufacturing. Manufacturers should provide clear working areas. For more info, click here
13. What materials are cable pits made from?
Cable pits are typically made from polymer concrete, cement concrete or plastic. Thin walled GRC pits should be avoided due to high porosity, poor resistance to biological attack and rough edges which may damage hands and cables. Lids are generally available in cement concrete, steel or polymer concrete. Access covers in steel or iron.
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14. How soil pressures can effect cable pits?
Soils apply lateral pressure on structures from their own weight, surface live loads (e.g. vehicles), expansive (soil) properties.
Resulting lateral earth pressure is exerted on the pit wall in the horizontal direction. Manufacturers should provide evidence of side wall strength if pits are not to be concrete encased. For more info, click here
15. How do I lock or secure a cable pit?People must be protected from cables and cables from people. Cable pits must address public and worker safety and general unauthorised access
In niche applications comply asset owners’ security requirements. E.g.. Government requirements for security (SCEC). For more info, click here
16. How do I install a cable pit?
A correctly installed enclosure is critical for long term performance. Depending on the application and pit material, an encasement of cement concrete and/or trafficable concrete collar may be required.
Some pits require bracing prior to compaction. Multiple conduit entries can compromise the strength of a pit and this must be compensated for. Manufacturers should provide typical installation drawings and installation methodologies as well as recommended minimum conduit spacing on a pit wall.
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17. How do I ensure cable pits are safe for the public?
Slip trips & falls can occur and electrocution, in rare occasions. Metal components within the enclosure should be kept away from electrical cables. The absence of locking bars are the best solution. If required, pits should be connected to the earthing structure of a building or construction via earthing strap 'eye'
The top surface of all lids and covers should meet the requirements of AS/NZS 4586 and HB 198 and most importantly provide the same slip resistance as the adjacent pavement. This is because differences in slip resistances can create slips and trips
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18. How do I ensure cable pits are safe for the work crews?Stopping foreign materials from entering the pit and ensuring safe lid lifting are the key.
Excessive ingress may make service enclosures hazardous. A degree of protection is required against objects, (needles, fingers etc) and is expressed as an IP (International Protection) rating to AS 60529. Lifting of lids for maintenance must be in accordance with the National Code of Practice for Manual Handling. Manufacturers should provide weights for all products and lifting devices should be independently certified. Heavy castings should have lifting anchors.
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19. Can cable pits be made waterproof?
Service enclosures are not designed to be waterproof. A reasonable degree of weather resistance can be achieved by sealing edges of covers by capping lifting holes each time the cover is removed for servicing. Entry holes for conduits should be capable of being sealed to prevent siltation. Pit drainage is recommended particularly for pits positioned at sag points.
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20. What is a split pit?
A split pit is a pit which is supplied as components to be assembled around pre-existing cables.
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21. What is a SIT pit?
SIT (Series Isolation Transformer) Pits are specially formulated to hold SITs for airfield runway lighting.For more info, click here
22. What is an earth rod pit?
This is a pit that protects the earth rod connection and makes it available for inspection.For more info, click here
23. What are some non-standard external cabling solutions
A couple of non-standard solutions include using culverts—U-shaped concrete channels with lids instead of pits and conduits to accommodate large cable sizes and quantities. Another approach is installing a large coil (loop) of cable at a midpoint in a client’s facility. This coil is labelled and left in place for future infrastructure installation, enabling connection at a later date without disrupting existing services.
24. Copper theft is now a significant concern when specifying cable trunking systems and service enclosures. What considerations can be taken to reduce the risk of copper theft?
Copper theft is widespread and costly. To reduce risk, various security products can be employed, such as PowerLok lids with replaceable security bolts and padlocks with master keys unique to asset owners. High-security (SCEC) enclosures, as used by government and defence sectors, are another option. Collaboration with road authorities and energy providers can also help in designing secure covers that mitigate theft risks.
25. How best can we coordinate underground services on Brownfield sites where as-built drawings may be incorrect?
In urban areas, the complexity of overlapping underground utilities such as sewage, water, gas, electrical, and communications must be carefully considered, as collisions and relocations are expensive. Best practice includes conducting a site survey using ground-penetrating radar (GPR) to locate existing underground services. Service locators then mark the ground surface to indicate the position of these services.
26. How do asset owners and project engineers balance durability and safety of cable enclosures with pressures for faster delivery and cost efficiency, especially in high-traffic urban environments?
Balancing long-term durability, safety, quick installation, and cost is challenging. Designers should carefully review site conditions and applications, understand traffic and vehicle loads, and select durable products suited to those conditions. Where possible, use manufacturers standard details for ease of application. Maintenance requirements and pedestrian safety should also be considered. Pre-cast options are ideal for rapid onsite installation and help balance these competing factors.
27. For custom-designed electrical pits, what are the considerations for the pit wall thickness design?
Custom-designed pits are typically larger than standard sizes such as 450x450, 600x600, or 900x900 clear openings. They are designed to provide access for large conduit entries or to house underground substations. These pits require structural engineering input to detail reinforcement and are commonly cast in situ, including access cover pockets for beams. ACO supplies large Rhinocast multi-part cover systems that include universal beams certified by structural engineers. Purchasing or designing multi-part systems through ACO comes with the assurance of engineering certification and testing.