Slab Leak Detection Specialists

🇬🇧 What is a slab leak? The UK translation

"Slab leak" is the term American plumbers use for a pipe leaking beneath a concrete slab foundation. In the UK we usually just say a leak under a concrete floor, but it is exactly the same problem: a water supply pipe or central heating pipe, buried in or under the solid floor of your home, has started to leak where you cannot see it or reach it.

Plenty of homes across Cornwall and Devon have pipework running through solid floors. From roughly the 1950s onwards, builders routinely laid copper and steel pipes directly into the screed, the cement layer on top of the concrete slab. Today's Water Supply (Water Fittings) Regulations say water fittings must not be embedded in a solid floor unless they are protected and accessible, but older properties were plumbed long before that rule existed. The result is a generation of houses with ageing metal pipes sealed inside their floors.

One important distinction before we go further. This page covers water supply and heating pipes that run under or through the slab. If the leak is in an underfloor heating loop itself, that is a different job with its own test methods, covered on our underfloor heating leak detection page.

🚨 Signs of a leak under your concrete floor

Because the pipe is hidden inside solid concrete, you never see the leak itself. You see its side effects, and they are worth taking seriously:

• A warm patch on the floor with no obvious cause, the classic sign of a hot water or heating pipe leaking below
• Damp flooring: wet patches on carpets, lifting vinyl or laminate, or tiles that sound hollow
• Moisture rising through the slab, which can also have other causes. Our guide to moisture coming up through a concrete floor explains how to tell a leak from condensation or rising damp
• An unexplained jump in your water bill or a water meter that keeps turning when everything is off
• Low water pressure at taps, or a boiler that keeps losing pressure
• Musty smells or mould: guidance from the US Environmental Protection Agency notes that mould can start growing on damp materials within 24 to 48 hours, so a long-running floor leak feeds it constantly

🔧 Why pipes under concrete slabs fail

A pipe inside a floor lives a harder life than one clipped to a wall, and a few well understood mechanisms account for most of the failures we find:

Corrosion. Cement-based screed and concrete can corrode unprotected copper and steel over time, which is exactly why current standards require embedded pipes to be wrapped or ducted. Older installations often have bare metal in direct contact with the screed, and decades of contact eventually produce pinholes.

Ground and building movement. Slabs, screeds and pipework all expand, contract and settle at slightly different rates. Joints and bends take the strain, and a soldered joint that has been flexed for thirty years can begin to weep.

Thermal movement and abrasion. Hot water and heating pipes expand and contract every time they heat up. Where a pipe rubs against hard aggregate inside the slab, the wall of the pipe slowly wears.

Installation faults. A joint that was imperfect on day one, or a pipe nicked during the original build, can take years to fail. When it does, the evidence is sealed under concrete.

None of this means your floor is doomed. It means that when symptoms appear, the leak needs locating precisely rather than guessed at, because every wrong guess is a hole in your floor.

🔍 How we pinpoint a slab leak through solid concrete

Concrete hides a leak from your eyes, but not from the right equipment. We start by pressure testing the system to confirm there is a live leak and which circuit it sits on: hot, cold or heating. Then we bring in the detection kit, choosing the combination that suits your floor and your pipework.

After more than 30 years finding leaks across Cornwall and Devon, we carry the full toolkit to every job, so the survey does not stall if the first method is inconclusive.

Acoustic listening

Water escaping from a pressurised pipe makes a distinctive noise, and that sound travels through concrete. Ground microphones and listening sticks amplify it so the search narrows to a small area of floor. Read more on our acoustic leak detection page.

Thermal imaging

Our FLIR cameras read the surface temperature of the floor. A leaking hot water or heating pipe warms the slab above it, and that warm plume shows up on screen without a single tile being lifted. See how thermal imaging leak detection works in practice.

Tracer gas

For cold pipes and the stubborn leaks nothing else can pin down, we drain the pipe and charge it with the industry standard tracer gas, a mix of 5 per cent hydrogen in 95 per cent nitrogen. It is non flammable and safe in use, and the hydrogen molecules are small enough to escape through the leak and rise through screed and concrete, where a sensitive detector picks them up at the surface. Our tracer gas leak detection page explains the method in full.

Moisture mapping

Moisture meter readings across the floor and the bottoms of walls let us trace the water's spread back to its source, and the readings go straight into your report as evidence.

Not sure the leak is under the floor at all? Symptoms like damp walls and high bills can come from leaks anywhere in the property, and our broader water leak detection service covers the whole house, not just the slab.

🧱 Repair access without wrecking your floor

The point of professional slab leak detection is what happens next. Because we mark the leak position precisely and photograph the evidence, the repair opens one small, deliberate area of floor directly over the fault, rather than a trench cut on a hunch.

Once the leak is exposed, there is usually a choice to make. Sometimes the right answer is repairing the pipe at the marked point. Sometimes, especially where an old embedded pipe has corroded in one place and is likely to fail in others, the better long term option is isolating the buried run and rerouting a new pipe above the slab. We explain both options on the day, with the findings in writing, so you and your plumber can decide with the facts in front of you.

🛡️ Insurance, trace and access

Escape of water is one of the most expensive home insurance problems in the UK. The Association of British Insurers has reported that these claims cost insurers around £1.8 million every day, and leaks sealed under concrete floors are a big contributor because they run unseen for so long.

The good news is that most UK buildings insurance policies include trace and access cover. In plain terms, it usually pays for professionally locating the leak and making good the damage caused by getting to it, such as the opened section of floor. It does not always cover repairing the faulty pipe itself, and limits vary by policy, so check your own wording. Our plain English guide to what trace and access cover is walks through how it works.

Every slab leak survey we carry out can come with an insurance approved report: photographs, thermal images, moisture readings and a description of the methods used, written for your insurer's claims process. When you are ready to book, our trace and access service handles the detection and the documentation in one visit.

📋 What to expect on the day

A typical survey is clean, quiet work. Nothing gets dug up or drilled to find the leak: the equipment does the searching, and your floor stays intact while it does.