Underfloor Heating Leak? Signs and How It Is Found

Reviewed by the DCI Leak Detection team · Last updated June 2026

An underfloor heating leak is unsettling, because the pipework is buried in or under the floor where you cannot see it. The good news is that a wet system gives off clear warning signs long before any real damage is done, and the leak can be traced to one spot without lifting the whole floor. This guide explains the signs to look for, the important difference between wet and electric systems, why you should not start digging, and how a leak in a buried circuit is found.

Signs of a wet underfloor heating leak

Wet underfloor heating, often shortened to UFH, pumps heated water through pipe circuits laid in or under the floor screed and fed from a manifold. Because it is a sealed system, water should not escape. When it does, a handful of signs tend to appear. One on its own can have other explanations, but two or three together point firmly at a leak.

The pressure clue is the one to trust most. A wet UFH circuit is part of the same sealed heating system as your radiators, and that system is designed to keep its pressure between top-ups. Heating manufacturers, including Vaillant and Ideal Heating, note that repeated pressure loss most often comes from a leak in the pipework, radiators or valves, though a failed expansion vessel or pressure relief valve can be to blame instead. That last point matters: not every pressure drop is a leak, which is exactly why the cause is worth confirming rather than guessing. Our article on why a boiler keeps losing pressure goes through the possibilities in more detail.

Wet vs electric underfloor heating

Before anything else, it is worth being clear about which type of underfloor heating you have, because only one of them can leak water.

• Wet (water) underfloor heating circulates warm water through plastic pipe circuits laid in or under the screed, heated by a boiler or heat pump and controlled at a manifold. This is the system that can leak, and the one this guide is about.
• Electric underfloor heating uses heating cables or mats laid under the floor finish. It carries no water at all, so it cannot spring a water leak. If electric UFH stops working, the cause is an electrical fault, a thermostat issue or a damaged cable, which is an electrician's job, not a leak detection one.

This distinction is set out clearly by underfloor heating specialists such as Warmup and consumer body Which?. If you are losing pressure, topping up the boiler, or seeing damp on the floor, you almost certainly have a wet system, since none of those things happen with electric heating.

Why you should not dig up the floor

When a leak is buried under screed and tiles, the instinct can be to start lifting flooring where the damp shows. Resist it. The damp patch on the surface is rarely directly above the leak. Water spreads sideways through screed and follows the path of least resistance before it reaches the surface, so the wettest spot can be some distance from the pipe that is actually leaking.

Digging up the floor on a guess is expensive, messy and often wrong. You can lift an area of tiles and screed only to find dry pipe, then have to do it again somewhere else. It also disturbs more of the floor than the repair itself ever needed to. The point of professional detection is to turn that guesswork into a single, confirmed location, so the floor is opened once, in the right place, and no further than necessary.

How leak detection pinpoints it under the screed

A wet UFH leak is exactly the kind of buried, hard-to-see problem that non-invasive leak detection is built for. A specialist combines several methods to confirm where the water is escaping before anything is opened up.

• Thermal imaging. A thermal camera reads small temperature differences across the floor. Heated water escaping into the screed creates a warm signature, and the loops of the heating circuit show up, which helps map the leak back to a single point.
• Pressure and leak testing. Isolating the UFH circuit and testing it under pressure shows whether it is holding or losing water, and can narrow the leak down to a particular loop on the manifold rather than the whole floor.
• Acoustic detection. Sensitive microphones pick up the faint sound a pressurised leak makes as water escapes, which helps place a leak in a buried pipe.
• Tracer gas. A safe gas is introduced into the drained pipework and rises to the surface at the exact point it is escaping, pinpointing slow or small leaks that other methods can miss.

Used together, these tools tell the engineer which circuit is leaking and where along it, so any opening up of the screed is a small, targeted access point over the leak. Specialists, including the Underfloor Heating Repair Company, confirm that thermal imaging, pressure testing and acoustic methods can locate a UFH leak without ripping up all the flooring. Our underfloor heating leak detection service uses this approach across Cornwall and Devon, and the same kit handles wider central heating leak detection on radiators and pipework too.

When to call a professional

Some pressure drops settle once a one-off cause is dealt with, such as bleeding trapped air after the system has been worked on. A genuine UFH leak will not fix itself. Call a professional when:

• the system keeps losing pressure and needs topping up repeatedly;
• you have cold spots, a damp floor patch or a warm patch that does not match where the heating runs;
• your water bills are creeping up with no change in usage;
• you have ruled out the obvious, such as a leaking radiator valve, and the pressure still drops;
• you need an insurer-ready report to claim for tracing and any damage.

On that last point, many home policies include trace and access cover, which pays to find a hidden leak and make good the damage caused by reaching it, with limits that typically start around five thousand pounds. It does not usually pay to repair the pipe itself, and cover varies by policy, so check yours. A proper report is what insurers look for, and a non-invasive trace keeps the access damage, and the eventual repair, as small as possible.

Acting early matters with underfloor heating. The longer a circuit leaks under the screed, the more water tracks through the floor build-up, and the more disruption the repair eventually causes. Finding the source quickly keeps the job contained.

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