How to Upgrade an Old Drainage System with 110mm Pipes

Upgrading an outdated drainage system is a great way to improve the management of wastewater and surface water drains in your home.

Older systems, especially those using clay or cast iron pipes, are prone to cracking, leaks, and collapse.

Switching to modern 110mm drainage pipes can enhance the system’s efficiency, prevent future issues, and ensure everything meets current standards.

This guide will walk you through the process of assessing your current setup and installing new pipes, ensuring your underground drainage system meets modern standards.

1. How do I know if my drainage system needs upgrading?

Before starting the project, you’ll need to assess your existing system thoroughly:

• Locate and inspect the pipes: Find all pipes, manhole covers, and drain connections. Look for signs of wear at ground level, like cracks or persistent dampness, which could signal problems underground.
• Check the materials: Older systems often have clay pipes or cast iron soil pipes, which are prone to breaking or corroding. If your system has these materials, it's a good idea to consider replacing them with 110mm PVC. PVC is durable, lightweight, and easier to install.
• Review compliance: Make sure your system follows modern regulations, like BS EN standards and Document H of the Building Regulations. These cover everything from pipe gradients to inspection chamber placements, ensuring your new system is up to code.

2. How do I plan for the upgrade?

Proper planning is key to a smooth drainage installation:

• Choose the right materials: Go with 110mm PVC pipes for the main drain pipe. For connections, you’ll need pipe fittings like push-fit or plain-ended pipes. The choice between these depends on how permanent you want the joints to be.
• Map your pipe layout: Plan the pipe run carefully. Sketch where the pipes will go, ensuring the right slope for efficient drainage. The invert level of the pipes is crucial to prevent blockages; it’s typically a 1:40 gradient for foul water and a 1:100 gradient for surface water drainage.
• Calculate pipe lengths: Measure the amount of underground pipe needed for the project, accounting for bends and changes in direction. For areas where the pipes must change direction or depth, you'll also need additional components like drainage bends, bottle gullies, and pipe fittings.
• Connecting to the existing system: You'll need special connection types if you’re joining new pipes to older materials like cast iron soil pipes or salt glaze clay pipes. Flexible couplings and rubber seals are ideal for creating watertight connections between different types of pipe.

For more information, you can also read our underground drainage installation guide.

3. What steps do I follow to install the new pipes?

Once your planning is complete, it’s time to install the system:

1. Excavate the old system: Carefully dig along the pipe run, exposing the old sewer pipes without damaging other underground utilities.
2. Install the new pipes: Lay the new 110mm PVC pipes in the trench, ensuring the fall is correct for waste or surface water. Connect the sections using pipe fittings like push-fit joints or ring seal fittings.
3. Add bends and pipes: For changes in direction, use Drainage Bends. If your system includes pipes from washing machines or kitchen sinks, make sure they connect properly to the soil pipe system. Don’t forget about vertical pipes like the soil stack pipe, which helps manage toilet waste.
4. Install inspection chambers: Place these at key intervals for easy maintenance. They should be located where pipes change direction or at significant invert levels. Make sure the chambers are level with the ground and accessible for future inspections.

4. What if my drainage system has special needs?

Not all properties are the same, so you might need a few adjustments:

• Commercial applications: For businesses, you may need larger pipes to handle greater water volumes or additional access points for regular maintenance.
• Managing different waste systems: Ensure that greywater from washing machines, kitchen sinks, and surface water drainage from rainwater pipes are properly directed. Older homes may not have been designed for modern waste systems, so you may need to separate the foul water and surface water.
• Mains drainage or private sewage treatment: If you’re connected to the main sewer system, check with your local authority to ensure compliance. If not, a sewage treatment plant may be required, which comes with its own set of rules for waste management.

5. What problems should I look out for?

Upgrading a drainage system can present some challenges:

• Blockages: This can happen if your pipes don’t have the right slope. Make sure your pipes are installed with a proper gradient to avoid clogs.
• Connection issues: When joining different types of pipe, such as clay and cast iron pipes, use flexible couplings to bridge the gap. This will help create a watertight seal.
• Regular maintenance: Once installed, keep an eye on the system. Clear out any debris from pipes, and regularly inspect manhole covers, soil vent pipes, and drainage gullies to ensure they remain in good condition.

6. How do I stay up to date with regulations and new products?

Keeping your system up to date is crucial:

• Follow the latest standards: Regulations, like BS EN, are updated regularly, so make sure your system complies with the most recent guidelines.
• Use innovative products: New products, such as lightweight plastic soil pipes and rainwater adaptors, are available to make installations easier and reduce maintenance.
• Search forums: Online communities can provide helpful advice if you're doing a DIY project. You can also stay informed about the latest news in drainage solutions, ensuring you make the best choices for your system.

Conclusion

Upgrading an old drainage system with 110mm pipes is an excellent way to improve your property’s waste and water management.

You can ensure a smooth installation by carefully planning the pipe run, selecting the right pipe fittings, and ensuring compliance with current regulations.

Whether connecting to a sewer system or managing waste from different-sized waste pipe systems, attention to detail guarantees an efficient system.

If you’re unsure, consult a professional or seek advice in DIY communities.