Soakaway installation

A soakaway is an underground chamber that collects surface water and lets it soak slowly into the surrounding ground. It is a common way to deal with rainwater from a driveway channel, a patio or a downpipe where there is no other suitable place for the water to go. Built well, it works out of sight for many years.

Gardenscape has provided hard landscaping and groundworks since 2007, and soakaways are often installed alongside new driveways, patios and drainage runs. If you want the background on how soakaways and sustainable drainage work in general, our soakaway and SuDS guide covers it. This page explains what installation involves.

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Will a soakaway work in your garden?

A soakaway only works if the ground can absorb water. Free-draining soils take water away quickly, while heavy clay can hold it for long periods. Before committing to a soakaway, the ground is usually tested by digging a trial hole, filling it with water and watching how quickly the level drops. That result guides the size and depth of the chamber, or shows that another approach would be better.

Position matters too. A soakaway should sit a sensible distance from the house and other buildings so water is not soaking towards foundations, and away from boundaries and existing drains. Trees, underground services and garden layout can all limit where it can go.

Crates or rubble filled

Traditional soakaways were simply a pit filled with broken rubble or stone. Many are now built from plastic crate units wrapped in a geotextile membrane. Crates hold far more water for their size than rubble, because most of the volume is open space, so the excavation can be smaller for the same capacity. The membrane stops soil washing in and clogging the chamber.

The incoming pipe enters the chamber from the channel drain, gully or downpipe, and the top is backfilled and finished with turf, gravel or paving. Some designs include an access point so the inlet can be checked in future.

What installation involves

Installation starts with locating services and agreeing the position. The pit is excavated to the depth and size needed, the base is levelled, the membrane is laid and the crates are assembled inside it. Pipework is laid at a steady fall from the water source, connected, and the membrane is folded over the top before backfilling in layers.

Digging out a soakaway produces a lot of spoil, so waste removal and access for machinery are a large part of the job. Narrow side passages can mean more digging by hand. Where a soakaway serves a new driveway, it is usually built at the same time as the drive so the pipe runs and levels are set out together.

What affects the cost

The size of the area being drained, the ground conditions, the depth and capacity required, the length of pipework and how much soil has to be taken away all affect the price. Reinstating a lawn or paving over the top adds to it. We look at the site and the drainage needs on a free site visit, then give one fixed written quote.

Your questions answered

How do I know if a soakaway will work?

The ground is tested by digging a trial hole, filling it with water and timing how quickly it drains. Heavy clay drains slowly and may need a larger chamber or a different solution.

How far from the house should a soakaway be?

It should be set a sensible distance from the house and other buildings so water does not soak towards foundations, and kept away from boundaries, drains and services.

Are crate soakaways better than rubble?

Plastic crates wrapped in membrane hold much more water for their size than rubble, so the pit can be smaller, and the membrane helps stop soil clogging the chamber.

What affects the cost of a soakaway?

The area being drained, ground conditions, chamber size and depth, pipe runs, spoil removal and reinstatement. We price it after a free site visit with one fixed written quote.