Rainwater Guttering System Guide | Plan, Choose & Install

Step-by-Step Advice for Planning a Complete PVC Guttering & Downpipe System

A properly designed rainwater guttering system helps protect your property by collecting rainwater from the roof and directing it safely into a suitable drainage system. Choosing the correct guttering profile, downpipe size and connecting fittings is essential for effective drainage and long-term performance.

Whether you're replacing an existing rainwater system, installing guttering on a new property or upgrading to a higher-capacity system, understanding the components and installation process can help you select the right products and avoid common fitting problems.

This Brissco step-by-step guide explains how to plan a PVC rainwater system, choose suitable FloPlast guttering and downpipes, identify essential fittings and prepare for installation.

Rainwater System Step-by-Step Diagram

Use the rainwater system diagram below to understand how guttering, outlets, downpipes and drainage components work together.

The diagram provides a useful visual reference when planning a new guttering installation or identifying the components needed to replace an existing system.

Step 1: Measure Your Roofline and Plan the Drainage

Before purchasing guttering, measure the length of each roofline where rainwater needs to be collected.

Identify roof corners, changes in direction, suitable outlet positions and the route each downpipe will follow.

Consider the effective roof area and expected rainfall, as these influence the gutter capacity and number of outlets required.

For larger roofs or properties exposed to heavy rainfall, a higher-capacity guttering system may be necessary.

Planning Tip: Sketch your roofline and mark the positions of gutter lengths, angles, unions, running outlets and downpipes before ordering materials.

Step 2: Choose the Right FloPlast Guttering System

FloPlast offers several PVC guttering profiles designed for different property types, roof sizes and drainage requirements.

FloPlast 112mm Half Round Guttering

A traditional curved guttering profile commonly used on domestic properties. Its simple appearance makes it suitable for many standard residential rainwater installations.

FloPlast Square Line Guttering

Square Line guttering features a clean, angular profile that complements contemporary buildings and modern roofline designs.

FloPlast 115mm Deepflow Guttering

Deepflow guttering provides increased rainwater capacity compared with standard Half Round systems, making it suitable for applications requiring additional drainage performance.

FloPlast Miniflo Guttering

Miniflo is a compact rainwater system suitable for smaller roof areas, including certain sheds, garages, garden buildings and outbuildings.

FloPlast Niagara Ogee Guttering

Niagara Ogee guttering combines a decorative profile with practical rainwater drainage performance, making it a popular choice for properties where appearance and functionality are equally important.

Choosing the correct system: Always check the manufacturer's rainwater capacity guidance, roof area calculations and outlet requirements rather than selecting gutter size by appearance alone.

Step 3: Identify the Guttering Components You Need

A complete rainwater system requires more than gutter lengths and downpipes. Each fitting plays an important role in connecting, supporting or directing rainwater through the system.

Essential Rainwater System Components

• Gutter Lengths: Collect rainwater from the roof and channel it towards the outlets.

• Fascia Brackets: Support the guttering and maintain the correct alignment and fall.

• Gutter Unions & Angles: Join gutter lengths and allow the system to follow changes in roofline direction.

• Running Outlets & Stop Ends: Connect guttering to downpipes and close the ends of gutter runs.

• Downpipes, Bends & Pipe Clips: Carry rainwater down the building and secure the pipework in position.

Depending on your installation, you may also need downpipe shoes, drainage adaptors, hoppers, gutter guards or rainwater collection accessories.

Ensure all components are compatible with the guttering profile and downpipe system you have selected.

Step 4: Plan the Position of Gutter Outlets and Downpipes

Running outlets collect rainwater from the guttering and direct it into the downpipe system.

Position outlets where rainwater can be discharged safely into a suitable drainage point, such as an approved surface water gully or rainwater collection system.

The number and position of outlets depend on roof size, gutter capacity, roof layout and the manufacturer's recommendations.

Where the outlet does not align directly with the wall, compatible offset bends can be used to connect the gutter outlet to the vertical downpipe.

Plan the downpipe route carefully to avoid unnecessary bends and ensure suitable access for future maintenance.

Step 5: Understand Gutter Bracket Spacing and Fall

Correct gutter bracket positioning is essential for supporting the system and allowing rainwater to drain towards the outlets.

Guttering is normally installed with a suitable fall towards the running outlet, although the exact requirement depends on the manufacturer's installation instructions.

Fascia brackets must be securely fixed to a suitable supporting surface and positioned at the recommended intervals for the selected gutter profile.

Additional support may be required around gutter angles, stop ends, outlets and other fittings.

Important: FloPlast bracket spacing and fall recommendations vary between systems. Always follow the latest installation guidance for your chosen gutter profile.

Step 6: Fit the Gutter Lengths and Connecting Fittings

Once the fascia brackets and running outlets are positioned, gutter lengths can be fitted into the supporting brackets and connected using compatible gutter unions.

Ensure gutter ends are clean, square and free from debris before fitting.

Most standard FloPlast PVC gutter systems use rubber-sealed joints designed to provide a watertight connection while allowing thermal expansion and contraction.

Follow the manufacturer's insertion marks and fitting instructions to ensure each gutter section is correctly positioned.

Fit compatible internal or external angles where the roofline changes direction and use suitable stop ends to complete the gutter runs.

Step 7: Install the Downpipes and Drainage Connections

Connect the downpipe to the running outlet using the appropriate bends and pipe sections.

Secure the downpipe to the wall using compatible pipe clips and suitable fixings at the manufacturer's recommended intervals.

Ensure the downpipe is correctly aligned and that sufficient allowance is made for thermal movement where required.

At the base of the downpipe, use a suitable downpipe shoe, drainage adaptor or other approved connection to direct rainwater safely into the drainage system.

Rainwater should not discharge directly against the building foundations.

Step 8: Check and Maintain Your Rainwater System

Once installation is complete, inspect all gutter brackets, unions, outlets, stop ends and downpipe connections.

Check that the guttering follows the intended fall and that all components are correctly seated and securely supported.

Where safe and practical, test the system with water to confirm that rainwater flows towards the outlets without leaking or overflowing.

Regular maintenance is also important. Inspect gutters periodically for leaves, moss, loose fittings and blocked outlets, particularly during autumn and after severe weather.

Suitable gutter guards and leaf protection accessories can help reduce the accumulation of larger debris, although routine cleaning may still be necessary.

Common Mistakes When Planning a Rainwater System

Choosing the wrong components or overlooking important installation requirements can result in poor drainage, leaking joints or unnecessary maintenance.

Common mistakes to avoid:

• Choosing Undersized Guttering: A system with insufficient capacity may overflow during heavy rainfall.

• Incorrect Outlet Positioning: Poorly positioned outlets can restrict drainage or require unnecessary downpipe bends.

• Mixing Incompatible Fittings: Different gutter profiles and manufacturers' components may not connect correctly.

• Insufficient Bracket Support: Incorrect bracket spacing can cause sagging and poor gutter alignment.

• Ignoring Thermal Expansion: PVC guttering needs suitable movement allowances to prevent stress on joints and fittings.

Careful planning and following the manufacturer's instructions will help achieve a more reliable rainwater drainage system.

Frequently Asked Questions About Rainwater Guttering Systems

What components do I need for a complete guttering system?

A typical PVC guttering system includes gutter lengths, fascia brackets, unions, angles, running outlets, stop ends, downpipes, bends and pipe clips. Additional fittings may be required depending on the roof layout and drainage connection.

What size guttering do I need for my house?

The correct size depends on the effective roof area, expected rainfall and number of outlets. Standard 112mm Half Round guttering is suitable for many domestic properties, while higher-capacity systems may be required for larger roofs.

How many downpipes do I need?

The number of downpipes depends on roof area, gutter capacity, rainfall intensity and outlet positions. Consult the manufacturer's capacity guidance to determine the appropriate arrangement for your property.

What is the difference between Half Round and Deepflow guttering?

Half Round guttering has a traditional curved profile commonly used on domestic properties. Deepflow guttering has a deeper profile designed to provide greater rainwater capacity for suitable applications.

Can I mix different guttering brands?

Some guttering products from different manufacturers may be compatible, but this should never be assumed. Check the exact profile, dimensions, jointing arrangement and manufacturer's compatibility guidance before connecting components.

Do PVC gutters need to slope towards the downpipe?

Guttering should be installed in accordance with the manufacturer's guidance to achieve effective drainage. Many systems require a fall towards the outlet, although the recommended gradient can vary by profile and installation arrangement.

How far apart should gutter brackets be fitted?

Bracket spacing depends on the gutter profile and manufacturer's instructions. Standard domestic systems may allow spacing up to approximately 1 metre, while some higher-capacity or specialist profiles require closer support.

Can I connect guttering to an existing underground drain?

Yes, where the existing drainage system is suitable for rainwater and the correct connection fittings are used. The drainage arrangement must comply with applicable requirements, and rainwater should not be connected to an unsuitable drainage system.

How do I stop leaves blocking my guttering?

Regular cleaning and suitable gutter protection accessories can help reduce blockages. Gutter guards, gutter brushes and debris interceptors can reduce the accumulation of larger leaves and debris but do not eliminate the need for maintenance.

Can I install a rainwater guttering system myself?

Competent DIY users may be able to install PVC guttering with suitable tools, safe access equipment and manufacturer guidance. However, working at roof level involves significant risks, and professional installation is recommended where safe access or experience is lacking.

Shop FloPlast Guttering & Downpipe Products at Brissco

At Brissco, we supply a comprehensive range of FloPlast PVC guttering, downpipes and rainwater fittings for domestic and commercial applications.

Our range includes Half Round, Square Line, Deepflow, Miniflo and Niagara Ogee guttering, together with compatible fascia brackets, running outlets, unions, stop ends, angles, downpipe clips and drainage accessories.

Whether you're planning a complete rainwater installation or replacing individual components, choosing the correct products will help ensure effective drainage and long-term performance.

Browse our Guttering & Downpipe range online or contact the Brissco team for advice on selecting compatible rainwater system components.

Installation guidance is general. Always refer to the latest FloPlast technical instructions and relevant building regulations. Work at height should only be undertaken with appropriate training, equipment and safety precautions.