With more than half (58%) of hidden leaks originating outside a property, landlords must remember to focus on the maintenance of pipework outside as well as inside the property, leak detection specialist Aspect has warned.

The company analysed more than 9,000 leak detection callouts across London and the South and East of England over a 12-month period, finding that the majority of leaksoccur in underground supply pipes outside the main building.

Landlords often focus on internal plumbing or heating systems when leaks occur, but the risk of underground leaks is they can go undetected for long periods, causing even more wastage and potential damage. Such pipes are typically buried beneath gardens, driveways or boundary lines, which means that leaks can develop without visible warning signs and often without tenants being aware.

However, such external supply pipes are typically the responsibility of the property owner rather than the water provider, which means landlords may be liable for both investigation and repair.

The high cost of a hidden leak

Analysis of recent customer cases by the company showed that hidden leaks can waste 56 litres of water per hour, typically costing around £150–£160 per month and hittingannual costs of £2,400–£3,000 if left unresolved.

Aspect also points out that while tenants may initially bear the cost of increased water usage in metered properties, unresolved leaks can lead to disputes, complaints and additional maintenance costs for landlords.

The renewed focus on property standards and repair timelines under the Renters’ Rights Act also highlights the ned for early identification of maintenance issues.

Neil Lampton, leak detection manager at Aspect, said: “Greater awareness of external supply pipes as a key risk area can help landlords take a more targeted and cost-effective approach to maintenance, particularly as they are responsible for them, not the water provider.”

Aspect recommends practical steps for landlords

• Implement clear reporting processes for tenants to flag sudden increases in water usage, pressure drops or unusually high bills
• Act promptly on alerts or communication from water suppliers
• Include external pipework in planned maintenance schedules, particularly in gardens and boundary areas
• Be aware that persistent boiler pressure loss may indicate a hidden leak
• Arrange specialist leak detection where no obvious internal issue can be identified