Commonly Asked Drainage Questions: Can I Run Rainwater Into Sewer UK?
Jiangyin Suofei Electronic Technology Co.,Ltd. , https://www.suofeiscales.com
June 06 07:21:20, 2025
A common question that often arises is whether it's acceptable to channel rainwater or similar types of surface water into shared sewers in the UK. This is a subject worth discussing because any drainage-related project you undertake must adhere to both local and national regulations.
Key Takeaways:
- Rainwater and wastewater should never be mixed in shared sewers in the UK as it can lead to pollution and disrupt the treatment process.
- Rainwater should ideally be directed to a separate area such as a ditch, drywell, headwall charge, soakaway crate system, or a rainwater harvesting system.
Surface water generally refers to water found above ground, which can include water from lakes and streams, but is most commonly associated with rainwater. If stormwater drains into the same place as wastewater or foul water, you must ensure that you’ve been explicitly permitted to mix them.
For instance, if rainwater from your property enters the same system as public sewers, it immediately interferes with the initial treatment stage. When the separation process has already occurred, combining these waters negates this effort, which is counterproductive since the goal is to send foul water to treatment plants. When rainwater and foul water mix, substances like oils and fats, which are usually filtered out, can pass through the system unfiltered. This can lead to pollution and potentially harm aquatic life. In extreme cases, your local water company might contact you, and if they find out that you've been sending rainwater into the foul water system without permission, you could face significant fines.
Many people don't realize how much water flows through their drainage systems daily. Being aware of the volume of water leaving your home can help prevent future issues. For example, in a typical three-bedroom house, under normal weather conditions, the average daily discharge is around 1 cubic meter. However, if there’s improper drainage in areas like the garden, combined with rainwater, this can increase to 20 cubic meters or more.
This highlights why it’s crucial to direct water to the correct location and avoid letting it flow into public sewers, as there’s a strong possibility that they’ll become overwhelmed, leading to pollution, flooding, or overflow.
If your property uses a combined underground drainage system, check out another one of our blog posts for detailed information.
Where should you direct your rainwater collected in drainage pipes? A common solution is a ditch or drywell, which is essentially a dug-out hole in the ground that remains mostly dry. The idea is to create a space where water can run off and soak into the surrounding soil to prevent flooding. The ditch or drywell can be lined with a non-woven geotextile membrane to minimize sediment buildup and allow water to drain properly. Additionally, using gravel in the ditch serves as an excellent absorption layer.
Another option is a headwall charge, which involves redirecting water toward a pre-existing waterway. To do this, you’d install a solid pipe, typically twin-wall drain pipes, towards the water source and surround the outlet section with concrete to protect the bank. Before installing a headwall charge, you’ll need to follow specific guidelines set by your local authorities, so it’s important to consult them first.
A soakaway system is another effective method, functioning like an underground reservoir designed to collect rainwater during heavy rains to reduce the risk of flooding. The soakaway crates are installed below ground level and wrapped in non-woven geotextile membranes to keep dirt and debris out. Using this fabric ensures that no debris enters the system while still allowing water to infiltrate back into the ground.
When considering where to direct your rainwater, it’s wise to consider your neighbors. Sending your unwanted rainwater their way isn’t ideal if they lack proper drainage measures, as it could damage their property. If you decide to connect to a foul drain system, ensure you’ve received approval from your local authorities. Additionally, consider the impact on wildlife—draining rainwater into wooded areas can harm tree root growth and damage animal habitats.
If anything in this post is unclear, feel free to reach out to our team with any questions. We’re here to assist!
Shop Soakaway Crates:
We offer various products to help manage rainwater effectively, including soakaway crates, impermeable membranes, and drainage catch pits. Each product is designed to meet specific drainage needs and comes with detailed specifications to ensure optimal performance. Check out our selection online and choose the best option for your requirements.