Hot Water System Leak Detection in Wandsworth

Symptoms

The occupant of a property in SW18 had been dealing with an unresolved leak for some time, with multiple companies attending the property in an attempt to locate the source. Despite these visits, the problem remained unidentified.

A letter from the Waterboard confirmed high water usage at the property, indicating an active and ongoing loss somewhere within the pipework.

The leak had not been pinpointed prior to this visit, leaving the customer without a clear diagnosis or repair path. Given that multiple attempts had already failed, a structured hot water leak detection approach was required — one that could isolate the system, apply tracer gas, and narrow the leak to a precise location.

An isolation valve beneath the kitchen sink was also found to be leaking, adding to the overall water loss at the property. The primary concern, however, was the suspected leak within the floor, which required a methodical investigation to confirm and access.

Methods Used

On arrival, the engineer discussed the history of the problem with the customer before conducting a pressure test on the pipework. This confirmed a leak on the hot pipe.

Tracer gas was then introduced into the system, which indicated the leak was in the floor and pointed to the nearest practical access point. This is a standard technique in hot water leak detection where a leak is concealed beneath a screed floor with no visible surface signs.

To access the leak, two kitchen units were removed and the floor was dug down through the tile and screed. During excavation, an electrical cable was struck; an electrician attended to isolate the cable safely before work could continue.

Once access was established, the leak was confirmed and a repair was attempted in copper. Due to the wet conditions at the repair site, a copper joint could not be made reliably, and the repair was completed in plastic instead.

Investigation Process

1. 1
   Initial assessment and pressure test

   The engineer arrived, discussed the history with the customer, and carried out a pressure test on the pipework. This confirmed an active leak on the hot pipe.

2. 2
   Tracer gas introduced

   Tracer gas was added to the system and indicated the hot pipe was leaking in the floor, with the nearest practical exit point identified for excavation.

3. 3
   Kitchen units removed and floor excavated

   Two kitchen units were removed to gain access. The floor was then dug down through the tile and into the screed to reach the leaking pipe.

4. 4
   Electrical cable struck and isolated

   During excavation, an electrical cable was caught. An electrician attended the property to isolate the cable, allowing work to continue safely.

5. 5
   Leak located and repair attempted in copper

   The leak was found on the hot pipe beneath the floor. A copper repair was attempted but could not be completed due to the wet conditions at the repair site.

6. 6
   Repair completed in plastic and pressure tested

   The repair was made using 15 mil plastic pipe, elbows, and inserts. The repaired section was pressure tested and confirmed to be holding.

7. 7
   Isolation valve under kitchen sink repaired

   An isolation valve beneath the kitchen sink that was also leaking was addressed as part of the overall works.

8. 8
   Customer briefed on findings and next steps

   The customer was present throughout and was informed of all findings. The engineer explained that the plastic repair in the floor requires the area to remain accessible and will need boxing in, with reinstatement of the kitchen, floor, and tiles handled by the insurer's claims process.

Result & Outcome

The leak was located on the hot pipe beneath the kitchen floor, beneath the screed. The position was confirmed through tracer gas and physical excavation, with the leak found at the point indicated by the gas trace. The repair was completed in plastic pipework — 15 mil pipe, elbows, and inserts — and pressure tested to confirm the system was sound. The leaking isolation valve under the kitchen sink was also resolved.

As is common with hot water leak detection jobs of this type, the plastic repair in the floor must remain accessible. The repaired section will need to be boxed in rather than buried, and the customer has been advised to monitor both the repair and the water meter while the insurance claims process is initiated to reinstate the kitchen units, floor screed, and tiles.

The customer was present throughout the investigation and repair, and was fully briefed on every finding. Multiple previous companies had been unable to locate this leak; the combination of pressure testing and tracer gas provided the precise location needed to carry out a definitive repair.