Hot Water System Leak Detection in Bath

Symptoms

The property in BS31 is a first-floor flat with two bedrooms, one bathroom, and a combi boiler. It had previously undergone a system conversion from an open vent cylinder setup, but not all of the old pipework had been removed during that work.

Hot water pipework from the original installation had been left in the ground, and the rest of the hot and cold pipework had been run up into the ceiling and back down.

Underneath the bath, the old hot pipework was still connected to the hot tap feed, with the new feed tee'd into it. A Ballofix isolation valve was present, switched off, with pipework disappearing into the ground — the only pipework running beneath the bathroom floor.

This arrangement meant a section of buried, redundant pipework remained under live pressure, making hot water leak detection necessary to establish exactly where the fault lay.

Methods Used

The investigation began at the external meter, which confirmed an active leak. Because the property had a history of open vent conversion with pipework left in the ground, the focus moved to tracing the buried hot water route beneath the bathroom floor.

Pressure testing was carried out first to confirm a leak in the hot pipework, followed by acoustic listening on the hallway and bathroom floors, which detected the sound of escaping water. Tracer gas was then introduced to pinpoint the precise location, with detection carried out downstairs where the gas surfaced at the leak point.

This methodical approach — pressure test, acoustics, then tracer gas — is standard practice in hot water leak detection where buried pipework cannot be visually inspected. Each method built on the last, narrowing the search area before committing to a precise location.

Investigation Process

1. 1
   Meter checked on arrival

   The external meter on the pavement was observed showing a small active leak, confirming water loss from the property.

2. 2
   Pipework configuration assessed

   Investigation revealed that hot water pipework from a previous open vent cylinder installation had been left in the ground. The rest of the hot and cold pipework ran up into the ceiling and back down.

3. 3
   Inspection beneath the bath

   Underneath the bath, the old hot pipework was found still connected to the hot tap feed, with the new feed tee'd in. A Ballofix isolation valve, switched off, led into the ground — the only pipework beneath the bathroom floor.

4. 4
   Pressure test carried out

   The hot feed was cut into and pressurised to 2 bar. A gradual drop in pressure was observed, confirming a leak in the buried hot pipework.

5. 5
   Acoustic listening on floors

   Acoustic equipment was deployed across the hallway and bathroom floors, and the sound of water could be heard within the floor structure.

6. 6
   Tracer gas introduced and traced

   Tracer gas was introduced at 2.4 bar and successfully traced to the leak area downstairs, identifying the precise location of the fault.

7. 7
   Repair carried out

   The old hot pipework was capped off and the hot tap feed was connected directly onto the new hot feed pipework, isolating and bypassing the buried redundant section.

Result & Outcome

The leak was located in the buried hot water pipework left over from the previous open vent cylinder installation — specifically traced to an area downstairs beneath the first-floor flat. Tracer gas surfacing at the leak point confirmed the precise location, removing any ambiguity about where excavation or remedial work would be needed.

The repair was carried out as part of the same visit. The old buried hot pipework was capped off, and the hot tap feed was reconnected directly onto the new hot feed pipework, eliminating the redundant buried section from the live system entirely. This resolves the root cause rather than simply isolating the symptom.

For the customer, the outcome of this hot water leak detection job is clear: the source of the water loss has been identified and the pipework reconfigured to remove the problematic buried run. There is no longer a live connection feeding the old underground pipe, and the meter reading should reflect the leak has stopped.