What is an underground drainage system?
An underground drainage system is designed to direct water away from buildings, roads and other infrastructure. It prevents flooding, soil erosion and damage to foundations, and plays an essential role in the overall health of a structure.
Underground drainage ranges from surface water drainage to soil drainage. Various components come together to form a working system, and their type and quality determine how effective it is.
Water management is not new. Ancient civilisations such as the Romans had intricate drainage systems, and advances in materials and methods have since shaped modern systems, but the core principle of guiding water efficiently has stayed the same.
Seen cracks at a home you are buying? Get a survey price for the home you are buying.
What are underground drains made of?
The three materials commonly found are clay, pitched fibre and UPVC.
| Material | Background | Characteristics given |
|---|---|---|
| Clay | Used for centuries | Natural resistance to chemicals, suiting varied ground conditions |
| Pitched fibre | A 20th-century product | Condition needs checking, as with any older pipe |
| UPVC | A modern material | Resists corrosion and copes with temperature swings, making it a popular choice |
Which parts of a drainage system need checking?
Every component needs attention, not just the pipes.
- Pipes: their internal condition, their gradients and their potential for sediment build-up need assessment, beyond a surface look.
- Manholes: their structural soundness, protective seals and alignment with the system's flow all matter.
- Inspection chambers: often overlooked, these are essential access points, especially in larger systems, and need periodic checks.
What problems can a failing drainage system cause?
A compromised drainage system can lead to flooding, soil erosion, foundation damage and, in older systems, asbestos exposure during repairs.
- Flooding causes visible damage and can disrupt local ecosystems, with long-term environmental effects.
- Soil erosion affects more than the look of a garden; it can upset the nutrient balance of the soil and affect local plants.
- Foundation damage carries structural risk, and moisture getting in can encourage mould growth, with health implications for occupants.
- Asbestos may be present, especially in older systems, and its potential health hazards call for care during repairs.
What affects the cost of drainage work?
A drainage system is a long-term commitment, and its costs fall into three areas:
- Materials: better materials cost more at first but can last longer.
- Labour: skilled professionals reduce future complications and the costs that come with them.
- Hidden costs: these include restoring gardens and landscaping, structural repairs, and even potential litigation over damage caused by inadequate drainage.
What does a CCTV drainage survey show?
A CCTV survey goes beyond basic fault detection: it can also identify potential issues so they can be dealt with before they become problems.
- Targeted repairs: with clear evidence, repair decisions are more targeted and unnecessary work is reduced.
- Useful records: survey records can help with long-term maintenance planning.
Why do drains need periodic inspection?
Routine checks are a strategy of prevention. Regular maintenance keeps the system working and can extend its lifespan, and preventive work, though it costs something each time, can help avoid larger repair bills.
Well-maintained systems also help prevent contamination. On a wider scale, efficient drainage protects roads, bridges and other public infrastructure from water damage.
What to do next
- Have the pipes, manholes and inspection chambers assessed, not just the visible surface.
- Arrange a CCTV survey to see the internal condition of the pipes.
- Take care with repairs to older systems, which may contain asbestos.
- Plan periodic inspections and maintenance to extend the system's life.
What a survey can — and cannot — tell you
A building survey provides an informed assessment of the visible condition of a property. Inspections are non-intrusive and limited to areas that are accessible at the time of inspection.
For drainage, a survey looks at the parts of the system that can be seen and identifies where a closer look below ground is justified.
The surveyor can look at and record:
- Visible manholes and inspection chambers and their general condition
- Signs of flooding, soil erosion or water-related damage around the building
- Visible signs of foundation damage or moisture getting into the structure
However, there are limitations to what a survey can determine without intrusive investigation.
- The internal condition of buried pipes, their gradients and any sediment build-up cannot be seen without a CCTV survey.
- The presence of asbestos in older drainage components cannot be confirmed by sight.
Where higher-risk indicators are identified, further specialist or intrusive investigation may be recommended.
Frequently asked questions
What does an underground drainage system do?
It directs water away from buildings, roads and other infrastructure, preventing flooding, soil erosion and foundation damage.
What are old drains made of?
Clay drains have been used for centuries, and pitched fibre pipes are a 20th-century product. UPVC is the modern material.
Can old drains contain asbestos?
Yes, especially in older systems. The potential health hazards from asbestos call for care during repairs.
What is the benefit of a CCTV drain survey?
It finds existing faults and can indicate developing problems, so repairs are better targeted. The records can also help with maintenance planning.
Can poor drainage damage foundations?
Yes. A compromised drainage system can lead to foundation damage, and moisture getting into the structure can encourage mould growth, with health implications for occupants.
