How to find the source of a leak before calling a professional

By the Málaga Urgente team · Updated 1 October 2026 · 8 min read

Why the stain is rarely right under the source

A leak is water getting in that shows up on a ceiling or wall. What you see, the stain, is the point where the water comes out to the surface, which does not always coincide with where it gets in. Water follows the path of least resistance: it travels through the slab, along a joist, inside a wall or following a pipe, and can cover several metres before showing.

That is why repairing "right above the stain" often fixes nothing. The first step in solving a leak is working out where the water comes from and whether it is a one-off entry (after rain) or a continuous one (a leaking pipe).

The most common causes of a leak

Although every case is different, most leaks have one of these sources:

• Roof. Broken tiles or tiles shifted by the wind, blocked valleys or gutters, and deteriorated flashings.
• Terrace or flat roof. Aged waterproofing, cracks, open joints or blocked drains that let water pool.
• Façade and windows. Cracks, deteriorated window seals or frames that do not fit properly.
• Water installation. Leaking pipes, poorly sealed joints or dripping valves.
• Stacks and drains. Breaks, loose joints or blockages that make them overflow.
• Bathrooms and kitchens above. Shower joints, traps, washing machines or the floor's own waterproofing.
• Condensation. Not an external water entry, but it can leave similar stains on ceilings and in corners.

What to do right away: safety first

If water is dripping right now, three things are worth doing as soon as possible:

1. Protect the electrics. If water is falling near lamps, sockets or the consumer unit, switch off the breaker for the affected circuit or the main switch. Do not touch wet installations with damp hands.
2. Contain the water. Put a bucket or container in place and protect floors and furniture. If the ceiling is bulging and full of water, do not puncture it suddenly: carefully make a small hole so it drains into a container.
3. Shut the main water valve if you suspect it comes from a pipe and the stain is growing fast.

Then take photos and video of the damage, dated if possible. They will help with the insurer and for explaining the problem to the technician.

How to find the source step by step

Simple checks can narrow down the diagnosis considerably before calling anyone:

1. Observe the pattern. A round stain with a clear edge usually points to a one-off entry; a wide, diffuse area may indicate condensation or a long water path.
2. Relate it to the rain. If it grows or appears only when it rains, it points to the roof, terrace, façade or windows. If it appears in any weather, it points to a pipe or a drain.
3. Do the meter test. Turn off all taps and appliances and see whether the water meter keeps turning. If it does, there is a leak in the installation.
4. Ask the neighbour above. If there is a home above, check whether they have a problem or have had recent works.
5. Check the terrace or roof. Look for standing water, leaves in the drains, cracks, open joints or shifted tiles.
6. Check seals and windows. Cracked seals or poorly fitted frames let water in with wind and rain.
7. Note how it develops. Mark the edge of the stain in pencil with the date to see whether it grows, and when.

If you want to do a water test, do it in stages, starting at the lowest area and moving up, waiting a while between each stage. If you do it the other way round, the water you have already added confuses the result.

How professionals locate a leak

When simple checks are not enough, there are techniques that locate the source with little or no building work:

• Moisture meters that detect the level of moisture in walls and ceilings without damaging them.
• Thermal imaging camera, which shows temperature differences associated with damp and leaking pipes.
• Pressure test on the water network to confirm whether there is a leak and in which section.
• Endoscopy with a small-diameter camera to look inside cavities and ducts.
• Tracer gas or dye in water circuits or drains to follow the route.

These techniques avoid "chasing walls blindly" and reduce the damage and cost of the repair. Once the source is located, it is repaired and then the damage to the finish is made good.

What you should not do about a leak

• Plugging without diagnosing. Sealing the stain or the visible point without knowing where the water comes from is usually wasted money: the water finds another way.
• Painting straight away. With a damp surface, paint blisters and the stain returns. You must wait for it to dry and for the source to be repaired.
• Chasing walls blindly. More damage than necessary is done and the point is often missed. Better to locate it first with measurement or thermal imaging.
• Using low-quality silicones or fillers on terraces and roofs. They last little and complicate a proper repair afterwards.
• Leaving it for later. A small leak can damage the slab, ruin the electrical installation and encourage mould. The sooner it is treated, the less it costs.
• Ignoring the electrical risk. If there is water near the installation, the priority is to cut the power to the affected circuit.

A good repair follows an order: locate the source, stop the water getting in, let the area dry and only then repair and paint the finish. Skipping a step usually means starting again.

Leaks on the Costa del Sol and in the Axarquía: what we see most

The climate and construction of the area explain some characteristic leaks:

• Heavy autumn rain. In the Mediterranean, episodes of heavy rain saturate drains and test terraces and roofs that have endured months of sun.
• Waterproofing worn out by the sun. Terrace membranes and paints dry out and crack after years of intense radiation.
• Wind. The levante and terral winds shift tiles and force water in through windows and flashings.
• Salt. Near the sea, it damages joints, balcony reinforcement and seals.
• Homes closed for months. A small leak in a second home can cause major damage before anyone sees it.

If the source is a terrace or façade, the solution usually involves waterproofing; if it is a pipe, our plumbers. To understand why a stain keeps coming back, see our guide on rising damp and salt damp.

Home and community insurance: how to act

Water damage is usually covered by home insurance, although the conditions depend on each policy. To avoid problems:

• Report the claim as soon as possible to your insurer and follow their instructions.
• Document the damage with photos and video, before repairing anything.
• Keep invoices for repairing the cause and the damage.
• If it comes from another home, talking to the neighbour and handling the claim between insurers usually speeds up the repair.
• If it comes from a shared element, such as the roof or façade, repair normally falls to the community: tell the administrator.

You do not need to wait for the insurer to respond before stopping the water or preventing more damage: acting quickly reduces the final cost.

When to call a professional

It is wise to call a technician if the stain is growing, if there is electrical risk, if the leak is continuous, if you have repaired it and the problem returns, or if you cannot find the source with simple checks.

On a visit we locate the source, explain what is happening and give you a fixed quote before starting. If it is urgent, we handle plumbing emergencies and electrical emergencies.

Quick questions

Why does the stain appear in a different place from the leak?

Because water travels through slabs, pipes, pillars and joints before reaching the surface. The visible point is usually lower down and some distance from the real source.

How do I know whether it is a pipe leak or rain seepage?

If it appears only when it rains, it points to the roof, terrace or façade. If it appears in any weather, or the water meter turns with everything off, it points to a pipe.

Can I paint over the stain?

Not until the source has been located and repaired and the area has dried. Painting over only hides the problem and the stain returns.

Is a leak near the lights dangerous?

Yes. Water near lamps, sockets or the consumer unit poses a risk of electric shock and short circuit. Switch off the breaker for the affected circuit or the main switch and call an electrician.

Who pays for repairing a leak?

It depends on the source: the owner if it is from their home, the neighbour if it comes from another, and the community if it comes from shared elements such as the roof or façade. Home insurance usually covers water damage; report it as soon as possible.

Keep reading

• Rising damp and salt damp on the Costa del Sol and the Axarquía
• Water leak or electrical fault at home: a quick action guide