Inspection, Maintenance and Repair of Rainwater Systems

If damage is identified during an inspection but the drainage system is otherwise performing adequately, general maintenance (such as decoration) and like for like repairs (for example, replacing a broken section) may be enough.

Access for maintenance and repairs is essential. In some instances, improvements to the system (such as adding rodding points) may be required, or a cherry picker may be needed for safe high-level access. The frequency of maintenance requires regular review, and the schedule may need to change to ensure optimum performance of the rainwater system.

It is important to assess the condition of rainwater systems during and after extreme weather events to identify any failures and plan for any necessary repairs or upgrades. If the rainwater system is failing to shed water effectively away from the building (inappropriate layout or detailing) or if it is overwhelmed during heavy downpours (insufficient system capacity), upgrades or alterations may be necessary to prevent water ingress and to improve the building's resilience to a changing climate.

Historic England's Maintenance Plans for Older Buildings gives further advice, and the Maintenance Checklist includes a non-exhaustive list of issues to be inspected.

Rainwater goods and gullies

When rainwater goods are fixed to the outside of a building (for example, external downpipes wall-mounted or set into a recess in the wall), a simple walk around the building may be enough to identify any failures. However, in the case of valley, box or parapet gutters, a visual inspection from ground level may not suffice, and high-level access for a closer assessment may be needed.

Occasionally, downpipes are embedded in the building fabric (built in and concealed) and so are not easily accessible. In such cases, it is essential to understand how the rainwater system was designed and where the downpipes are located. Appropriate access will be needed to carry out the necessary inspections, maintenance and repair works.

Downpipes that connect directly to below ground drains may become blocked over time. To facilitate maintenance and repair, it is advisable to fit a downpipe shoe that discharges openly into a surface gully.

Where gullies are present, the effective discharge of downpipes into gullies is critical for the appropriate functioning of the rainwater system. Blockages can be prevented by installing grilles, which can be easily cleared of leaves and debris.

Clearing rainwater goods and gullies regularly will ensure they function as intended for as long as possible.

Below ground drains

Below ground drains collect water from rainwater goods and can also collect ground level runoff from the areas around a building. They should be inspected and maintained to the same degree as rainwater goods and gullies. If drains break (because of impact or tree root disturbance, for example) or suffer joint failure, water may saturate the surrounding soil and potentially impact the building fabric and foundations.

Below ground drains may feed directly into a soakaway or other infiltration system, into a nearby watercourse or into a sewer (separate, combined or partially combined).

When a soakaway is part of the drainage system, it is essential to check it is still performing appropriately and has not silted up. If a soakaway has silted up and failed, it is advisable to excavate it and repair or replace as necessary. Its life could be prolonged by incorporating inspection hatches to allow for routine clearance and maintenance. New soakaways must be designed with the help of a specialist engineer.

In a flood zone, installing non-return valves will protect the system from backflow during a flood event. However, non-return valves may not always be appropriate, including in areas where they can silt up and block quickly. Where they are not appropriate, it is essential to ensure that below ground drains can be easily accessed for maintenance and repair.