Case Study: Rats Accessing Yard via Unprotected Inspection Chamber Vent NE3

Summary

An inspection identified an unprotected inspection chamber vent that was allowing rats to exit the drainage system directly into the customer’s yard. A galvanised mesh cover was installed on site to prevent further access.

Reported problem

The customer reported repeated rat activity within the rear yard, with sightings continuing despite no obvious surface burrows, food sources, or harbourage being present.

Inspection findings

During the external inspection, a ground-level inspection chamber vent was identified. The vent was missing its mesh cover, leaving a clear, unrestricted opening directly into the drainage system.

The chamber itself showed no signs of collapse or blockage. However, the position and condition of the vent provided a direct route for rats to exit the drains and access the yard.

Photographs were taken to document the defect and its relationship to surrounding ground levels and structures.

Analysis

Inspection chamber vents in older, Victorian-era drainage systems were designed to allow sewer gases to escape and to balance air pressure within the drains. These vents were often left open or fitted with light mesh, which has commonly corroded or been removed over time.

In this case, the vent was still functioning as intended for airflow, but the missing mesh meant it was also acting as a direct access point for rats moving between the sewer network and the external environment.

Treating surface activity alone would not have resolved the issue, as the source of activity was the drainage system itself rather than the yard.

Resolution

While on site, a galvanised mesh cover was securely fitted over the inspection chamber vent. This maintained the required ventilation function while preventing rodent access.

The completed proofing work was photographed and recorded within the inspection report.

Outcome

By installing a galvanised mesh cover, the access route allowing rats to exit the drainage system and enter the yard was eliminated. This addressed the underlying cause of activity without the need for ongoing surface control.

Key takeaway

Unprotected drainage vents can provide direct access for rats; fitting suitable mesh protection can permanently remove this pathway while retaining ventilation.