Does your garden or outdoor space suffer from flooding or get waterlogged in some areas? If the answer is yes, today’s guest post explains how a soakaway might be the answer to the problem.
A soakaway is, in a nutshell, a hole that’s dug into the ground and filled with coarse stone and rubble. It’s there to enable surface water to seep back into the earth, and is usually part of a full drainage system; there’s almost always a land drainage pipe leading into the soakaway to guide the water in.
As well as dealing with excess rainwater effectively, the added bonus of a soakaway is that it has a low environmental impact. It uses natural materials, and deals with the water pretty much where it falls and collects, so there’s no need for processing or chemical treatments.
If you think a soakaway could be beneficial in your outdoor space, here’s what you need to consider.
Do you need a soakaway?
If you have standing water or waterlogged areas, a soakaway is a good solution. Leave that water where it is and you risk water damage to your property, not to mention the impact on the look and usability of your outdoor space. If the waterlogged area is in a landscaping project or a driveway, you should use a soakaway rather than overburden your existing drainage system. You should never direct excess water into a cess pit or septic tank, for example.
Before deciding to go for a soakaway, check the composition of your soil. It must be granular in order to provide good drainage. A soakaway isn’t going to work if your soil is heavy on clay; you’ll end up with a pond!
How to do it
Thinking ahead and making plans is the best way to avoid time-consuming and potentially very expensive mistakes.
You’ll need to check your local building regulations before you start any work, and if you’re doing any hard landscaping you need to provide a sustainable drainage system (SUDS) to deal with your surface water. Look at Planning Policy Statement 25, which is about flood risks; it asks for surface water to be collected and dealt with where it falls. If you can reuse it, that’s ideal. Soakaways fit this bill quite well, especially as they also have a low environmental impact.
Where should I place my soakaway?
Most local authorities ask for soakaways to be at least five metres away from a habitable building. They should also, if possible, be at the lowest-lying area of your land; not only does this mean less digging, but it’ll be more efficient. If placing it there means excessively long or convoluted pipes, then it might not be the best location – it’s a balancing act.
You also need to work out where your water table is by digging an exploratory pit. The water table needs to be below your planned soakaway, or the collected water won’t be able to drain away.
The pipe that goes into the soakaway needs to be at least 75mm in diameter, as 75mm is the minimum diameter for surface water drainage. 100mm is recommended, though, so aim for this.
Your pipe needs to “fall” at a 1 in 40 grade; for every four metres of pipe it should slope downwards by 100mm. You can hand-dig the trench, or use a mini-digger.
How big does the soakaway need to be?
Your soakaway should be at least one cubic metre, and be below the bottom of the feeder pipe. If there’s a lot of water and it doesn’t drain too quickly, then it should be bigger.
When it comes to the hardcore infill, it should totally surround the pipe and rise to around 100mm above it. You should place an impervious layer on top of the stone rubble – thick membrane or even concrete is ideal – before finishing it off with topsoil and turf to hide everything.
And there you have it – soakaways demystified! Could a soakaway be the answer to waterlogging problems in your garden?
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