9 Signs of a Hidden Water Leak in Your Flat

1. The water meter keeps turning

With every tap closed, the meter should be still. If the small dial moves, water is escaping. It is the one sign that proves a leak exists — see how to read your water meter.

2. A higher water bill

A bill that jumps without any change in how you live. Check that it is not a correction after estimated bills, then do the meter test. See average water bill in Portugal.

3. Damp patches and stains

On walls next to bathrooms and kitchens, at the base of walls, or on the ceiling below a bathroom. A stain that grows, or that has a darker edge, is active.

4. Bubbling, flaking or swollen paint and plaster

Water behind paint pushes it off the wall. Swelling skirting boards and door frames near bathrooms are another version of the same sign.

5. Loose, cracked or hollow tiles

Tiles that sound hollow when tapped, move, or have dark grout lines can mean water is getting under them — often from a leaking shower tray or supply pipe. See leaking shower tray.

6. Musty smell and mould in one spot

Condensation causes mould in cold corners and around windows, spread out. A leak causes mould in one area, often at a specific height, and keeps coming back after cleaning. See damp and mould: leak or condensation.

7. Low pressure

Water escaping on the way can reduce pressure at the taps. On its own, low pressure is more often limescale — see low water pressure in the shower.

8. A warm spot on the floor

A leaking hot-water pipe under the floor can make a patch of tiles warm to the touch, and makes the water heater run more than usual.

9. The neighbour downstairs

Often the first person to notice a leak in your bathroom is the person below you. If they report a stain, take it seriously even if you see nothing. See leak from the flat upstairs.

What to do next

Do the meter test to confirm. Check the easy suspects: toilet cisterns, the water heater safety valve, hoses under sinks and behind appliances.

If those are fine, the leak is inside a wall or floor. Leak detection finds the exact spot so only a small area is opened.

Where hidden leaks most often are

Behind the shower mixer, where hot and cold pipes run in the wall. Under the bathroom floor, especially near the toilet and shower. Behind the kitchen units, at the dishwasher and sink connections. Around the water heater. Along old iron pipe runs, at the threaded joints.

Knowing this helps interpret where the damp shows up.

How a leak detection visit works

We start with the meter and the visible fittings, then isolate and pressure-test the hot and cold circuits separately. That tells us which circuit is losing water. From there we narrow down the position using the layout of the pipes and the signs on walls and floors, and open only where the leak is.

You get a written description of where it was and what was done — useful for landlords and insurers.

Why acting early saves money

A leak that has run for weeks soaks screeds, swells wooden floors, damages the flat below and grows mould behind tiles. The repair to the pipe may be the same size either way; the damage around it is not.

Frequently asked questions