Electronic Leak Detection: What the Readings Mean and When to Doubt Them
Electronic leak detection produces readings: a gauge figure, a moisture number, a temperature picture, a gas level, a sound trace. A reading is evidence, not a verdict. This page shows what each one means, which ordinary conditions fake it, and what confirms it. A visit is charged at £180 an hour. No VAT is charged.
What the visit covers
- Each reading taken in a sound area as well as the suspect one, so the figure has something to be compared with
- A second, different reading before any number is called a finding
- A report that lists every reading, including the ones that showed nothing
- A plain statement of which readings were doubtful and why
Published prices
What it costs
- Fixed-price leak location package
- The package gives one fixed price, known before the visit, to locate a leak in one property using whichever methods the leak needs.
- £580Fixed price
Or by the hour
- Standard leak detection
- General water leak detection in a property.
- £180an hour
No VAT is charged
A fixed hourly rate that cannot rise on the day
No find, no fee applies when a live leak inside your own property cannot be located. No find, no fee in full
Order of work
Take a baseline
A reading in a place thought dry or sound comes first. Without it a moisture figure, a temperature or a gas level has nothing to be measured against.
Take the suspect reading
The same instrument is used on the area under suspicion, in the same way, so the difference between the two is what counts.
Confirm with a different physical signal
A cool patch is checked with a moisture meter. A sound is checked with a pressure test. See how to read a leak detection report for how this appears in the write-up.
Reading to meaning
The word electronic suggests a detector that points at the leak. In practice each instrument measures one physical quantity and the reading only becomes useful against a reference. This table sets out what each one gives you.
| Reading | What it looks like | What it suggests | Confirm it with |
|---|---|---|---|
| Gauge figure | A fall in bar, or a steady needle, over a set time on an isolated circuit | That circuit is losing water, or is not | A second hold test, or a different circuit |
| Moisture figure | A number or bar on a display, set against a dry area nearby | The material holds more water than its surroundings | A thermal image or a pressure test |
| Temperature picture | A colour scale over the surface, with a cool or warm patch | A pattern that may follow a pipe or a wet area | A moisture reading on the same patch |
| Gas level | Parts per million against the background in the room | The nearest point to a leak on a gas-filled, isolated pipe | A repeat sweep, or a camera at that point |
| Sound trace | A level that peaks between two sensor positions | A pressurised pipe losing water near the peak | Gas at the same spot, or a pressure test |
| Camera image | A live picture from inside a void | What is physically there at that spot | Running water while the picture is watched |
Readings that look like a leak and are not
Most wrong calls come from a reading taken at face value. These are the common false alarms, and each is why a second signal is required. How deep and how reliably a moisture meter reads depends on its type, which pin versus pinless moisture meters explains, and a phone thermal camera shows less than a survey camera does.
| Reading | Looks like | Can also be |
|---|---|---|
| High moisture figure | A leaking pipe behind the wall | Rain, condensation, a bridged damp course or old damp that has not dried |
| Cool patch on a thermal image | Wet plaster or a wet floor | Missing insulation, a cold bridge or a draught |
| Falling gauge | A leak on the pipe | A fitting settling, an expansion vessel or a tap dripping on the circuit |
| Gas reading above background | The leak position | Gas that has travelled along a void and surfaced somewhere else |
| Sound peak | The leak position | Water running in another pipe, or noise carried along a rigid run |
A reading that did not agree with the story
On a two-visit job in WC1X the first visit recorded a loss on the hot supply. The second visit held pressure on hot and cold twice and tracer gas was negative. The numbers disagreed with the first reading, so the report moved the likely source to the shower area instead of claiming a position the readings did not support.
That is what a cross-check is for. A falling gauge against a holding one is shown side by side in the pressure gauge notes from the field, and the report says how sure a position is, as how accurate leak detection is explains. Where two signals cannot be made to agree, the report says so. The ordered steps of a survey are set out on non-invasive leak detection, and the instruments themselves are described, kit by kit, on the equipment page.
What it costs
Instrument time is part of the visit, charged at £180 an hour. No VAT is charged, and the rate is a fixed hourly rate that cannot rise on the day. Tracer gas work adds £80 for each gas cylinder, as set out on the tracer gas page.
Where the instruments are used on one property, the whole visit can instead be the £580 package for locating the leak. No find, no fee applies when a live leak inside your own property cannot be located. See the no find, no fee terms.
Questions customers ask
Is there one electronic detector that finds any leak?
No. Each instrument senses one thing, and each has conditions where it reads nothing. A reading is checked against a second, different one.
Can the readings be wrong?
Yes. A moisture figure with no dry reference means little, and a thermal image can show a cool patch with no water behind it. That is why every figure is compared and confirmed.
Will I see the readings?
The report lists them against each instrument, including those that showed nothing, so you or a plumber can see what each result rested on. It is also the record an insurer assesses if a claim is made. Cover depends on the policy and the insurer decides; see leak detection report for insurers.
How is a visit charged?
At £180 an hour, or as the £580 fixed-price package for one property. No VAT is charged.