A hidden leak on the incoming water supply can waste a surprising amount of water before there is any obvious puddle or damp patch. This mains leak guide is for homeowners who have noticed a high bill, falling water pressure or a water meter that will not stop moving – and want clear, practical next steps without unnecessary digging.
For wider household water-saving advice, see the Spanish Ministry of Consumer Affairs guidance.
The mains pipe is the supply line carrying water from the meter to your home. This mains leak guide supports practical checks before repair work begins. If it leaks underground, beneath a driveway or under a floor, the water may disappear into the ground rather than show itself indoors. Act promptly to protect your property and limit water waste. Early action can also lead to a smaller, more affordable repair.
Mains leak guide: what makes a supply leak different?
A leak on internal pipework normally affects a particular area of the home, such as a bathroom, kitchen or utility room. A mains leak is often harder to spot because it can be outside the building or below the property before the water reaches your internal plumbing.
The exact responsibility for pipework can depend on where the leak sits, the type of supply and local arrangements. In many homes, the section from the meter towards the property is the owner’s responsibility. A specialist leak detection visit can establish where the water escapes. You then have useful evidence before arranging repairs or speaking to your water provider.
Mains leaks are not always dramatic. A small crack can leak steadily for weeks. The same applies to a failing joint or corroded pipe. In areas with very dry ground, such as much of the Costa Blanca, water can drain away quickly and leave few visible signs at the surface.
Mains leak guide: the warning signs to take seriously
One sign on its own does not prove a leak. A pattern of changes, however, deserves attention. The most reliable early clue is a water meter that continues to register usage when every tap, appliance and irrigation system is switched off.
You may also notice a larger-than-usual water bill or inconsistent pressure at taps. A boiler may repeatedly need topping up. You might also hear water moving through the pipework. Outside, look for a persistently damp patch, unusually green growth, loose paving or soil that has begun to sink. Water emerging from a wall, driveway or garden is an urgent warning. However, it may appear some distance from the actual break.
Holiday homes need particular care. A property left empty during a warm spell may leak for much longer than an occupied home. If a neighbour, keyholder or cleaner reports a damp smell, arrange an assessment quickly. The same applies to an outdoor wet area or an unusual meter reading. Do not wait until your next visit.
A simple meter check
Start by making sure nobody is using water. Turn off taps, washing machines, dishwashers, pool top-up systems, garden irrigation and automatic ice makers. Then take a photograph of the meter reading, including the small flow indicator if fitted.
Wait for 30 to 60 minutes without using any water and check it again. If the numbers or indicator have moved, water is flowing somewhere. This does not confirm that the leak is on the mains pipe, but it gives a strong reason to investigate.
If the meter is in a shared area or serves more than one property, do not assume the result points to your own pipework. A qualified engineer can isolate and test sections properly, avoiding guesswork.
What to do if you suspect a leak
If water is entering the home, affecting electrics, lifting flooring or causing rapid flooding, turn off the internal stopcock if it is safe to do so. Do not touch electrical equipment in a wet area. Keep clear when water is close to sockets, wiring or a consumer unit. Seek urgent professional help.
For a suspected underground leak without flooding, avoid digging straight away. Excavation based only on a damp patch can damage cables, pipes, paving and landscaping. The source may be several metres away. It can also turn a controlled repair into a much larger reinstatement job.
Instead, note what you have seen: meter readings, the location of wet patches, changes in pressure and when the issue first appeared. This information helps the engineer choose the most suitable test and can reduce the time needed on site.
How non-invasive mains leak detection works
A reliable diagnosis should narrow down the location before repair work starts. It should also confirm the type of problem. The best method depends on the pipe material, its depth, whether the line is pressurised, the ground conditions and how accessible the pipework is.
Pressure testing
Water pressure testing checks whether a closed section of pipework can hold pressure over time. A pressure drop may indicate a leak, although it must be interpreted carefully. Temperature changes, connected appliances and poorly isolated valves can affect results. Therefore, this test works best as part of a wider investigation.
Acoustic leak detection
Pressurised water escaping from a pipe creates vibration and sound. Sensitive acoustic equipment can listen for the characteristic noise through the ground, walls or accessible fittings. This is often highly effective on metallic pipes and can help trace a route without lifting large areas of paving.
It is not a one-size-fits-all answer. Plastic pipe can transmit less sound, and busy roads, pumps or strong wind can create background noise. An experienced engineer will assess the conditions rather than promise that one tool alone will solve every case.
Gas trace detection
For difficult or deeply concealed leaks, an engineer may introduce a safe trace gas into an isolated pipe section. The gas rises through soil, screed or small gaps in the surface, where specialist sensors can detect it. This method is useful when a pipe runs under flooring, concrete or landscaped ground. It can work even when no water appears at the surface.
Compressed air and dye testing
Compressed air testing can help identify loss from isolated pipework and is useful where water testing is impractical. Dye tracing may be used where water is escaping into a visible route, helping confirm where it travels through a wall, floor or external area. These techniques are selected for the property, not simply used because they are available.
The aim is always the same: locate the source as accurately as possible, mark the likely repair point and minimise disruption to your home.
Why finding the source first saves money
A general plumber is the right choice for many visible leaks, such as a dripping tap, failed toilet valve or leaking radiator. But when water is hidden beneath a slab, garden or driveway, repair without accurate detection can become expensive trial and error.
Targeted detection helps a repairer open a smaller area. They can order suitable materials and focus on the defective section. It also provides reassurance when the fault is not where you first expected. A damp internal wall, for example, may be caused by an external supply leak travelling beneath the floor rather than a problem in the wall itself.
At Water Leak Services Spain, our engineers use non-invasive methods to locate hidden water loss with minimum disruption. Our no find, no fee promise is designed to give homeowners confidence that the focus is on a clear result, not speculative excavation.
When to arrange urgent help
Do not wait for a leak to become visible if the meter test suggests constant water use, your bill has jumped sharply or water pressure has changed suddenly. Act quickly if you see ground movement or persistent damp around foundations. Mould with no obvious cause also needs attention. Water near electrical areas requires urgent help.
Fast action is particularly worthwhile before leaving a property empty, or where a leak may be affecting neighbours, shared areas or an underfloor space. Homeowners in Torrevieja, Orihuela Costa and nearby areas can also face long periods of intense heat, when unnoticed water loss is both costly and difficult to spot at the surface.
Can I keep using water while a mains leak is investigated?
It depends on the severity and location of the leak. If there is no flooding and the supply remains safe, limited use may be possible. However, reducing water use can limit damage and makes testing more accurate. Follow the advice given after the initial assessment.
Will leak detection damage my driveway or floor?
Professional non-invasive detection is intended to avoid unnecessary damage. There may still be a small opening needed once the leak has been pinpointed and a repair is required, but accurate location should greatly reduce the area disturbed.
Does a high water bill always mean a leak?
No. Seasonal irrigation, guests, a faulty toilet cistern, pool use and meter-reading changes can all increase consumption. A controlled meter test and targeted investigation separate these possibilities from a concealed leak.
This mains leak guide gives you a clear starting point, but a mains leak does not improve with time. If your meter keeps moving when the property is quiet, treat it as a useful warning rather than a mystery to live with. Early, accurate detection gives you the calmest route to protecting your home.