The French drain is one of civil engineering's most enduring and effective solutions — a technology essentially unchanged since the 19th century that remains the go-to answer for garden drainage problems across Hampshire and Dorset. Here is a clear explanation of how they work and when they are the right answer.
How a French Drain Works
A French drain is a trench filled with clean gravel or crushed stone, usually containing a perforated pipe at the bottom. Water enters the gravel from the surrounding soil, flows through the gravel and into the pipe, then travels along the pipe to a soakaway or drainage outlet.
- Trench depth: typically 600–900mm
- Pipe: 100mm perforated pipe wrapped in geotextile sock
- Fill material: 20mm clean stone or pea shingle
- Outlet: soakaway pit, existing drain or ditch
- Surface: topsoil and turf over the top, or gravel left exposed
When a French Drain Is the Right Answer
French drains work best for intercepting surface and near-surface water movement — for example, at the base of a slope, along a fence line that collects water, or across a lawn that pools after rain. They are less effective where the problem is a high water table rather than water movement.
Cost and Installation
A typical garden French drain of 10–15 metres costs £800–£2,000 installed in Hampshire depending on the depth, access and outfall requirements. Most installations take one to two days and cause minimal disruption to the surrounding garden.
A&T Landscapes installs French drains across Hampshire, Dorset and Wiltshire. Call 07735 916029 for a drainage assessment and free quote.