What is a soakaway? Drainage pros reveal how this system could be the solution to standing water in your garden

Effective drainage around the home isn't the most glamorous of topics, but it's hugely important to ensure that water drains away from your home effectively. You might have even heard some of the terminology before, like a soakaway, but not really understand what a soakaway is.

Getting clued up on what soakaways are and how they work could make a big difference to your home's drainage efficiency this year. In short, soakaways are pits in the ground that help with the drainage of excess rainwater. They can be helpful if you're looking to improve drainage in your lawn, and they're particularly beneficial for homes in areas that are prone to flooding.

We've spoken to the experts to determine what a soakaway actually is (as well as some other soakaway FAQs), and put all their advice together to help you decide if this is the right solution for your home

What is a soakaway?

Soakaways are a large hole in the ground that help to drain away excess rainwater, making them an ideal measure for flood-proofing gardens. Occasionally they are also used for the disposal of effluent from septic tanks.

'Essentially, a soakaway is part of a below-ground system and consists of a pit filled with a highly voided material,' Martin Lambley, senior product manager for Urban Climate Resilience at Wavin explains.

'Traditionally they were constructed using materials such as large, crushed stones or hardcore, but are now more frequently constructed using plastic crates.'

How do soakaways work?

The crates used to form a soakaway are wrapped in a permeable filter fabric which allows water out, but doesn’t allow surrounding soil in. 'How they actually work is fairly simple and is informed by the natural water cycle,' Martin explains. 'The surface water collected from the property is fed into the soakaway and, as it rains, water is collected into the soakaway and allowed to infiltrate into the surrounding soil.'

According to Martin, the rate of infiltration is a function of the soil: 'Sandy soils have a faster infiltration rate and would therefore need a smaller soakaway, whereas if you want to improve drainage in clay soil, a larger soakaway would be required, because this type of soil drains more slowly.'

In the context of home properties, soakaways tend to be relatively small. They're usually installed within the garden, and it's recommended that they are at least 5m away from the property and 2.5m from a boundary.

While soakaways can be a great addition to a property, they're only really necessary for homes that struggle to manage water drainage. They're definitely something to consider if your garden remains saturated for a while following periods of heavy rainfall, or likewise, if your home has inadequate drainage and you're noticing things like damp basements and cracks in the brickwork.

Can I install a soakaway myself?

Installing a soakaway can be a fairly simple process, as it usually involves digging a hole in the ground that is then backfilled with material. You'd need to get the relevant supplies, but if you're confident with DIY, you can give it a go.

'Before installing a soakaway, you should first check if the ground beneath its proposed location is permeable by conducting a soil percolation test,' says Jess Thomas, director of Drainage Central. 'This test is essential, as the soakaway will not be useful if your soil does not allow water to seep into it.'

A soil percolation test measures how quickly water drains into the ground, and you can find out more about how to do this online. The most time-consuming part of installing a soakaway is digging the actual hole. It needs to be fairly large, and you might want to recruit some helping hands for this part of the process.

It's then a case of filling the whole with large plastic crates, which can be assembled two or three deep. The crates will create a large volume of space for rainwater to collect.

What you'll need to install a soakaway

FAQs

What happens when a soakaway is full?

When a soakaway is full, it means that the water collected cannot drain any further and therefore has nowhere else to go. 'This can result in water pooling on the surface of the ground above the soakaway and potentially flooding,' Max Ledsham, drainage expert from Kingfisher Direct explains.

'In the worst case scenario the groundwater that has accumulated may increase and even intrude into the property and result in more serious damage,' Max adds.

If a soakaway isn't properly maintained, it will become oversaturated, and collected water will be unable to infiltrate surrounding soil.

'To avoid this, good design practice and regular maintenance is key to guarantee soakaways are performing to the best possible standard,' Martin from Wavis says.

'Common techniques to ensure their smooth running include installing a silt trap in the system to ensure debris like sand, soil and leaves can’t enter the crate and eventually cause a blockage.'

How do you know if your property has a soakaway?

Soakaways are usually discreet in their design, so they aren't always the easiest to identify. To find out whether your property has one, drainage expert Max recommends to look at your property's rainwater downpipes and identify where they go.

'If your downpipes lead to an area of your lawn that is slightly sunken in then it's likely that your garden has an underground drainage system. In addition, if your property has a soakaway this may be established in the deeds, so it's therefore a good idea to consult the property deeds to check.'