Wet patch in your garden? You might have an underground leak

A single wet patch in your garden which does not dry out with the rest is unusual. And it could be trying to tell you something important – there is an underground leak.

Early warning signs come when an area remains constantly moist – even during dry spells of weather or when no watering has taken place.

What then should you do? Here is some advice for determining if your garden wet patch is caused by an underground leak – and actions to take if it is.

What causes underground leaks?

Underground leaks typically stem from problems in plumbing or irrigation systems. Here are the most common sources:

• Damaged water pipes: Residential water supply lines made of copper, plastic or other metal piping can fail for multiple reasons. Corrosion, cracking, ground movement, tree root ingress and freezing and thawing cycles can all lead to an underground leak.

• Leaking sewer lines: Cracks in a sewer line can release moisture into the surrounding soil. Whilst major sewer leaks will come with a foul odour helping to identify the reason for a garden wet patch, the only sign of a smaller leak can be damp, spongy or muddy soil.

• Broken irrigation lines: If your garden has a built-in irrigation system, a broken or disconnected pipe or sprinkler head can lead to water accumulating in one spot instead of being evenly distributed.

How to determine if you have an underground leak

If you are unsure whether the wet patch in your garden is due to a leak or if it is because of another drainage issue, look for these telltale signs:

• The patch remains wet long after rainfall or watering.
• There is an increase in your water bill without a known reason.
• You notice a drop in water pressure in your home.
• Grass or plants in that spot are growing much faster or are noticeably greener than the surrounding areas.
• You hear a faint hissing or bubbling sound when standing near the area.
• There is a musty or sewage-like smell coming from the soil.

Why an underground leak is a problem

Underground leaks are more than just a nuisance — they can lead to serious consequences if not dealt with:

• Structural damage: If the leak is near the foundations of a building, it could eventually cause structural issues.

• Soil erosion: Constant water flow underground can erode soil, creating sinkholes and destabilising walkways and patios.

• Mould and mildew: Excess moisture can encourage mould growth in nearby structures. It can even affect indoor air quality if the leak is near your house.

• Higher utility bills: A leaking water pipe wastes water and increases your water bill over time.

What to do if you suspect an underground leak

If you suspect the wet patch in your garden is caused by an underground leak, here are some steps to follow:

• Stop watering and monitor: Pause any irrigation or watering in the area for a few days and observe whether the patch dries up. If not, it is more likely a leak.

• Call a professional to assess whether it is a leak: A licensed plumber or leak detection specialist can use tools like acoustic sensors or ground-penetrating radar to locate a leak. This can help avoid unnecessarily digging up a garden.

• Repair the underground leak ASAP: If a leak is identified, it should be repaired quickly to avoid further damage and water waste. Some issues can be DIY fixes, like cracked clay drainage pipe repair. A major leak in a sewer line, however, would require a professional.

Take a wet patch in your garden seriously

A wet patch in your garden might seem like a minor oddity. But it could be a sign of a hidden leak that is silently wasting water and causing damage underground.

Staying vigilant and addressing the issue quickly can save you from costly repairs and ensure your garden stays healthy for the right reasons.