Leaks in Heating and Radiators: Detection and Solutions Without Construction

Data updated in September 2026 — Information verified with internal data from Telefuga and real reviews from Google Maps.

Why are leaks in heating systems more dangerous than other water leaks?

Leaks in heating systems cause damage 40-60% faster than leaks in cold water pipes, and they have a significantly higher repair cost if not detected in time. The reason is chemical and physical: hot water (40-60°C in radiators, 30-45°C in underfloor heating) accelerates the corrosion of pipes and metal fittings, dissolves more minerals, and facilitates the proliferation of anaerobic bacteria that attack the joints.

At Telefuga, we have been detecting leaks in all types of installations for 16 years, with 38,000 leaks resolved and a rating of 4.8/5 on Google (319 reviews). Of all the leaks we handle, those in heating are the most urgent and the hardest to diagnose without professional equipment, as the water circulates under the floor or embedded in walls where it is completely invisible.

This article explains how a heating system works, the types of leaks that can occur, how to identify them by their symptoms, and how Telefuga locates them without breaking the floor or walls thanks to infrared thermography.

How a heating system works: understanding to diagnose

Before discussing leaks, it is essential to understand how the installation works. A hot water heating system has the following components:

• Boiler or heat pump: Heats the water in the circuit to the programmed temperature
• Closed pipe circuit: Transports hot water from the boiler to the emitters (radiators or underfloor heating) and returns it for reheating
• Emitters: Aluminum, steel, or cast iron radiators, or underfloor heating pipes (cross-linked polyethylene PEX or polybutylene PB)
• Expansion tank: Absorbs the expansion of water when heated, preventing overpressure
• Safety valves: Automatically release water if the pressure exceeds the limit (normally 3 bar)
• Air vents: Allow trapped air to be removed from the circuit
• Filling valve: Allows water to be replenished when the pressure drops too low

The system operates as a closed circuit: under normal conditions, it should not lose a drop of water. If the circuit pressure drops, there are two possible causes: trapped air (solved by bleeding) or a leak (requires detection and repair).

Types of leaks in heating: where and why they occur

1. Leaks in the closed pipe circuit

The pipes connecting the boiler to the radiators or underfloor heating are the most extensive component of the system and, therefore, the most statistically likely to develop a leak. The main causes are:

• Internal corrosion: Dissolved oxygen in the water corrodes steel and copper pipes from the inside. This is the most common cause in installations over 15-20 years old
• External corrosion: Pipes embedded in acidic mortars or in contact with incompatible materials
• Mechanical fatigue: Thermal expansion/contraction cycles (every time the heating turns on and off) generate mechanical stress on welds and elbows
• Installation defects: Poor welds, loose connections, pipes without clearance for expansion

2. Leaks in underfloor heating

Underfloor heating uses cross-linked polyethylene (PEX) or polybutylene (PB) pipes that snake under the flooring in circuits of up to 100 meters per room. Leaks in underfloor heating are the hardest to detect and locate for several reasons:

• The pipes are buried under 5-8 cm of mortar, tiles, and sometimes additional insulation
• The circuits snake in long and winding paths
• The leak may manifest meters away from the actual break point
• Hot water partially evaporates within the screed, hiding the true extent of the loss

Common causes of leaks in underfloor heating:

• Accidental perforation during renovations (drilling, nailing, screwing into the floor without checking the layout)
• Material defect or faulty joint in the manifold
• Degradation of the pipe due to untreated water (lime, excessive chlorine)
• Structural movements (differential settling) that stress the pipes at joint crossings

3. Leaks in radiators

Radiators are the most accessible points of the system and, therefore, the easiest to inspect. Typical leaks in radiators occur at:

• Inlet and return valves: O-rings and packing nuts deteriorate with thermal cycles
• Air vents: A loose or damaged air vent drips constantly. This is the easiest leak to repair
• Joints between elements: In aluminum radiators, the joints between elements can fail due to galvanic corrosion
• Radiator body: Internal corrosion that perforates the radiator wall (more common in steel radiators)

4. Leaks in the boiler

The boiler is a pressurized unit with multiple joints, seals, and components that can develop leaks:

• Heat exchanger: Corrosion from hard water (high lime content) or failures in water treatment
• Safety valve: If it frequently activates, it may lose tightness (also, its repeated activations indicate an overpressure problem)
• Hydraulic connections: Inlet/outlet fittings can loosen with the vibrations of the boiler
• Expansion tank: The internal membrane can break, causing the safety valve to activate due to overpressure

5. Leaks in valves and fittings

The entire system has shut-off valves, stop valves, thermostatic valves, manifolds, branches, and numerous fittings. Each of them has seals that degrade over time and temperature. Leaks in fittings are generally small but constant.

Symptoms of leaks in heating: how to detect them yourself

These are the symptoms that should alert you to a possible leak in your heating system:

1. Constant pressure loss in the boiler

This is the most classic and reliable symptom. The normal pressure of a domestic heating circuit when cold is 1.0-1.5 bar (and rises to 1.5-2.0 bar when the water is heated). If you need to refill the circuit with the filling valve more than once a month, you have a leak.

Filling Frequency	Probable Diagnosis	Recommended Action
Once at the start of the season	Normal (dissolved air)	Bleed radiators and refill
1-2 times a month	Possible small leak	Monitor and check accessible valves
Weekly	Confirmed leak	Urgent professional detection
Daily	Severe leak	24h Emergency — risk of structural damage

Telefuga Fact: 65% of the heating leaks we detect started as a “slow pressure loss” that the owner compensated for by refilling the circuit every few weeks. That refill water, rich in oxygen and lime, accelerated corrosion even more, turning a micro-leak into a larger leak within months.

2. Irregular heating: cold rooms

If one or more rooms are not heating properly while the rest of the circuit works well, there may be a leak in the section supplying that area. The leak reduces the flow of hot water reaching the affected emitters.

Attention: Before assuming a leak, rule out that the problem is trapped air (bleed the affected radiators) or a faulty thermostatic valve.

3. Moisture stains on the floor or baseboards

When there is underfloor heating, leaks can manifest as:

• Dark spots on tiles or parquet
• Moisture at the base of the walls (baseboards)
• Bubbling or peeling of laminate or wooden floors
• White efflorescence (mineral salts) on the joints of the tiles

These symptoms usually appear weeks or months after the leak started, when the water has already saturated the screed.

4. Noises in the installation

A leak in the closed circuit introduces air into the system (when refilling) and can cause:

• Gurgling: Air bubbles circulating through the pipes
• Water hammer: Compressed air in pockets causes metallic knocks as water circulates
• Hissing: The sound of water escaping through a small crack, audible on quiet nights

5. Hot floor in a specific spot

If you notice a spot on the floor that is noticeably hotter than the rest (outside the normal pattern of underfloor heating), it may indicate that hot water is leaking and accumulating under the tile at that point.

6. Increase in gas bill

A leak forces the boiler to constantly heat the replacement water (which enters cold from the mains), increasing gas consumption. An increase of 15-25% in the gas bill without a change in usage habits is suspicious.

Infrared thermography: the revolution in leak detection in heating

Infrared thermography is the most powerful tool available for detecting leaks in heating systems, especially in underfloor heating. Its operation is particularly effective in these systems because it takes advantage of the characteristic that makes these leaks dangerous: the water is hot.

How thermography sees the circuit under the floor

When the heating is on, hot water circulates through the pipes embedded in the screed, heating the surface of the floor above. The thermal camera “sees” this heat as lines or coils of elevated temperature against the cooler background of the floor. This allows us to:

• Trace the complete path of the circuit without installation plans (which often do not exist or are lost)
• Identify interruptions in the layout: If the hot circuit “disappears” at one point and reappears later, the water is leaking in that area
• Detect abnormal heat accumulations: A “hot spot” under the floor indicates leaked water accumulating outside the pipe
• Locate the exact point of the leak with a precision of ±15 cm, sufficient to perform a minimal excavation

Optimal conditions for thermography in heating

To achieve the best results, at Telefuga we follow a specific protocol:

1. The owner is asked to turn on the heating to maximum at least 2 hours before the inspection
2. Carpets, furniture, and objects covering the floor in suspicious areas are removed
3. The thermal image of the entire floor is recorded, room by room
4. The thermal pattern is compared with the expected layout of the circuit
5. Anomalies are identified: interruptions, accumulations, dispersions

Thermography is especially reliable in underfloor heating because the temperature difference between the pipe (35-45°C) and the surrounding screed (20-25°C) creates a very clear thermal contrast, even through 5-8 cm of mortar and tiles.

Telefuga's process for leaks in heating: different from the standard

Leaks in heating require a different approach than standard leaks in cold water pipes or drainage. Our specific protocol for heating includes:

Step 1: Technical interview (15 minutes)

Before we travel, our technician collects critical information by phone: type of system (radiators/underfloor heating), brand and model of the boiler, age of the installation, frequency of pressure loss, observed symptoms, and whether there is a layout plan of the installation.

Step 2: Pressure test of the circuit (30 minutes)

With the heating off and cold, we pressurize the circuit to 2.5-3 bar (above the working pressure) and monitor the pressure drop for 15-20 minutes. This confirms the existence of the leak and gives an idea of its magnitude.

In systems with multiple circuits (underfloor heating with multi-way manifold), we pressurize each circuit individually to isolate which one has the leak.

Step 3: Infrared thermography with the circuit hot (45-60 minutes)

We set the heating to maximum and perform a complete thermal scan. The high-resolution camera (<0.05°C sensitivity) allows us to visualize the layout of the pipes and detect thermal anomalies with millimeter precision.

Step 4: Confirmation with geophone (15-20 minutes)

In the area identified by thermography, the electronic geophone amplifies the characteristic sound of the leak: a hissing or dripping that is clearly perceived with high-sensitivity headphones. In very small leaks, we slightly pressurize the circuit to increase the sound.

Step 5: Marking and minimal excavation (30 minutes)

We mark the exact point of the leak on the floor with a precision of ±15 cm. The excavation (controlled opening of the floor) is done in a minimal area of 4.80x30 cm, as opposed to the traditional alternative of lifting square meters of floor.

Step 6: Repair (1-3 hours depending on complexity)

Once located, the repair depends on the type of leak:

• PEX underfloor heating: Cut the damaged section and splice with pressure fittings or electrofusion
• Copper pipe: Welding or replacement of the section
• Steel pipe: Replacement of the section (repairs in steel corrode quickly if materials are mixed)
• Valve or fitting: Replacement of the defective part

Leak season in heating: October-March

Leaks in heating have a marked seasonality. At Telefuga, 75% of our leak detections in heating are concentrated between October and March, coinciding with the heating season in Murcia, Alicante, Valencia, Albacete, and Almería.

The reason is twofold:

1. Leaks only manifest when the system is in use. During the warm months (April-September), the circuit is off and micro leaks do not lose water (no pressure or circulation). When the heating is turned on in autumn, the pressure and temperature reactivate the leak.
2. The thermal expansion/contraction cycles of seasonal startup are the most aggressive. After 6 months of inactivity, the pipes are cold and contracted. When the heating is turned on, they expand sharply, stressing weakened welds and joints.

Monthly distribution of leak detections in heating (Telefuga data)

Month	% of annual detections	Observations
October	12%	Start of the season, first thermal stress
November	15%	First month of intensive use
December	14%	Continuous use, leaks become evident
January	16%	Peak — maximum heating demand
February	11%	Still intensive use
March	7%	Decrease in use
April-September	25% total	Residual leaks detected during renovations or inspections

Prices for leak detection and repair in heating

Service	Indicative Price	Includes
Heating leak detection (radiators)	From 150€	Pressure test + thermography + geophone + report
Underfloor heating leak detection	From 200€	Pressure by circuit + complete thermography + geophone + report
Repair of underfloor heating pipe	300-800€	Minimal excavation + repair + floor replacement
Repair of leak in radiator/valve	80-250€	Replacement of component + system bleeding
Heating expert report (insurance)	From 200€	Technical documentation with thermal images

These prices are indicative for the area of Murcia, Alicante, Valencia, Albacete, and Almería. Request a personalized quote for your specific case.

Real case: leak in underfloor heating detected with thermography

We share a representative case of our experience in detecting leaks in heating:

Situation: Single-family home in Albacete, built in 2008, with underfloor heating throughout the ground floor (120 m²). The owner had been refilling the circuit every 4-5 days for two winters. Their installer had told them it was “normal” to lose some pressure and had changed the expansion tank (without result).

Telefuga Diagnosis:

1. Pressure test: The circuit lost 0.4 bar in 15 minutes. Significant leak confirmed.
2. Circuit isolation: The manifold had 6 circuits. Each was pressurized individually: the loss was concentrated in circuit 3 (main living room).
3. Infrared thermography: With circuit 3 on, the camera clearly showed the hot coil. 3.5 meters from the south wall, the hot trace “expanded” into a diffuse spot about 60 cm in diameter: hot water accumulating outside the pipe.
4. Geophone: Confirmed a soft but clear hissing at the marked point.

Repair: Excavation of 4.85x35 cm in the living room floor. A 16 mm PEX pipe was found with a 1.5 mm perforation caused by a screw that someone had driven in years ago (probably when installing a piece of furniture). The damaged section (15 cm) was cut and spliced with pressure fittings. Post-repair pressure test: 0 bar loss in 30 minutes.

Total cost: 420€ (detection + repair + tile replacement).

Estimated savings: The owner had already spent 180€ on replacing the expansion tank (unnecessary), and we estimate that the excess gas consumption from constantly refilling with cold water cost them about 15-20€/month during the heating season.

Why constant refilling worsens the leak

Many owners adopt the habit of “refilling when the pressure drops” as a temporary solution. This is a serious mistake for several reasons:

1. Mains water contains oxygen and lime. A properly sealed closed circuit gradually loses dissolved oxygen (it is consumed in the initial oxidation reactions). Every time you refill, you introduce fresh oxygen that reactivates corrosion. A steel pipe in a closed circuit without refills can last 40-50 years. With frequent refills, corrosion accelerates exponentially.

2. Lime deposits in the boiler heat exchanger. Mains water in areas like Murcia or Alicante is hard (250-400 mg/L of CaCO3). Each refill adds lime that deposits in the exchanger, reducing the boiler's efficiency and, in extreme cases, clogging it.

3. The leak never repairs itself. Corrosion and hydraulic erosion only worsen over time. What is currently a micro-leak of 50 mL/hour can become a leak of 500 mL/hour in 6 months.

4. Escaped water causes collateral damage. Water escaping from the circuit does not disappear: it accumulates in the screed, saturates the mortar, corrodes steel reinforcements in the slab, damages insulation, and can cause dampness in the lower floor.

Preventive maintenance: how to avoid leaks in heating

The best leak is the one that never occurs. Basic preventive maintenance can prevent 80% of leaks in heating:

Annual review of the installation (September-October)

Before turning on the heating each autumn:

1. Check the cold pressure: It should be between 1.0 and 1.5 bar. If it is below 0.8 bar after summer, there may be a slow leak
2. Bleed all radiators: Open each air vent until water comes out without bubbles. Start with the radiators farthest from the boiler
3. Refill the circuit after bleeding: Open the filling valve until reaching 1.2-1.5 bar. Close it afterwards
4. Visually inspect: Check all accessible valves, radiators, connections, and the boiler for drips, rust stains, or efflorescence
5. Turn on the heating for 2-3 hours: Check that all radiators heat evenly and that there are no unusual noises
6. Check the pressure again: If it has dropped significantly compared to the cold reading (>0.2 bar), there may be a leak

Correct bleeding of radiators

Bleeding is the most important and often neglected maintenance operation. A radiator with trapped air not only heats less, but the air accelerates the internal corrosion of the system.

Recommended frequency: At the start of the season and once more in mid-winter (January). If you need to bleed more frequently, the system is introducing air, indicating a leak or a faulty expansion tank.

Correct pressure of the circuit

System State	Normal Pressure	Observations
Cold (heating off)	1.0-1.5 bar	The recommended filling pressure is 1.2 bar
Hot (heating on)	1.5-2.0 bar	Water expands when heated, increasing pressure
Maximum allowed	3.0 bar	Above this, the safety valve activates
Low pressure alarm	<0.8 bar	The boiler may block for safety

Treatment of circuit water

In new installations or when making a repair, we recommend adding corrosion inhibitor to the circuit water. These products (based on molybdates or nitrites) create a protective film inside the pipes that dramatically reduces corrosion. Approximate cost: 25-40€ per household.

Periodic professional inspections

Every 3-5 years, especially in installations over 10 years old, a professional inspection with preventive pressure testing is recommended. It is much more economical to detect a weakness in the circuit before it becomes an active leak.

Leaks in heating and home insurance

Most home insurance policies cover water damage, including leaks in heating. However, there are important nuances:

• The detection: Many policies cover the cost of professional detection (look for “search and location of leaks” in your policy)
• The repair of the pipe: Generally covered as “repair of the cause of the claim”
• The aesthetic damage: Replacement of flooring, painting, etc., normally covered
• Negligence: If the insurance proves that the leak had been unattended for months (refilling the circuit instead of repairing), it could reduce or deny compensation

The expert report from Telefuga is the key document for processing the claim with your insurer. It includes thermal images, exact location of the leak, probable cause, and repair estimate.

Conclusion

Leaks in heating and radiators are a silent problem that can cause serious structural damage if not detected in time. The constant pressure loss in the boiler is the clearest alarm signal: if you need to refill the circuit more than once a month, you have a leak and each refill is making it worse.

Infrared thermography has transformed leak detection in heating: what previously required lifting square meters of floor blindly is now resolved with a thermal image that shows exactly where the leak is.

Telefuga has been detecting leaks in heating systems in Murcia, Alicante, Valencia, Albacete, and Almería for 16 years, with 38,000 leaks resolved and a success rate of 98%. Our heating leak detection service starts from 150€ and includes infrared thermography, pressure testing, and a technical report.

Request your heating diagnosis → Don't wait for the leak to worsen. We detect and repair without lifting the entire floor. Also, check our page on water leak detection and our geophone detection service.