A Guide To Soakaway Systems

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If you have surface water pooling around buildings due to heavy rainfall, installing a soakaway could solve some of your drainage problems. A soakaway is basically a big hole dug into a garden that collects excess rainwater and makes it drain away into the ground more gradually, rather than letting it all rush in and lead to a waterlogged garden.

As well as being a cheaper drainage option, soakaways are straightforward to install, and because they’re so simple and yard-friendly are one of the most eco-friendly drainage methods out there. Here’s a quick rundown on what they’re for, what you’ll need to make one, how to install one, and how to keep it lasting for years.

Using Soakaways

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A soakaway is usually built at least 5 to 10 metres away from a building, and is designed to have rainwater directed to it from the existing drainage system. From there, it can percolate into the ground at a slower rate. Usually crates are used and with the help of a permeable membrane they’ll provide a large void or tank underground that the water will drain from slowly, meaning the yard doesn’t get waterlogged and start to leave pools of surface water. If property is on a tilt, you’ll want to dig out the pit at a lower point to make sure water can flow in. Quick note – never empty sewage into your system, as it will only lead to a blockage and a nasty lawn, or rainwater into the sewage system as this is illegal.

It’s important to note before you start ordering materials that you need to check your local planning regulations, as some properties are in protected areas and aren’t allowed to have soakaways. You might also want to check your soil’s absorption rate with a percolation test – if the soil is too soft, it won’t release water, meaning that there’s no point investing in a soakaway!

The Parts of a Soakaway

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While soakaways aren’t a complicated type of drainage system, they still need a few different parts to function. Here’s a quick checklist of what makes up a typical soakaway system:

Soakaway Crate

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The soakaway crates makes up the main part of your soakaway system, and is what collects the water and allows it to drain out at a better rate. Soakaway crates are modular, meaning that you can stack them and put them next to each other depending on the size and structure of your soakaway, and can be used with permeable membranes and pipes to help reduce the surface water in the surrounding area. You can buy a soakaway crate kit to make your life easier, as this comes with everything but the drainage pipe and gravel.

Geotextile Membrane

header image for what are geotextile membranes, geotextiles explained blog post at easymerchant

These are a kind of permeable geotextile membrane that stop debris from getting into your soakaway crate while still allowing water to seep through. For a soakaway system, you’ll want to get hold of a non-woven membrane – just line the sides of your crate with it and staple into place! Make sure you do not use a woven membrane with a soakaway system as it’ll hold onto the water and not allow it to drain properly.

Waterproof tape

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Waterproof tape is used to join the membrane.


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Once your non woven geotextile membrane lined crate is in place, you’ll need to fill the back and sides of the crate in with some shingle, and put an extra layer on top to then cover over with soil and whatever other landscaping material you’re using.

Gravel / Top Soil

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Soakaway crates used to be filled with gravel and rubble instead of crates back in the day – now, we think it’s best to stick to using it as a finishing layer on top of your system. Not only does it look good in your garden, but it’s simple to maintain and can always be topped up no problem.

Silt Trap

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This is optional, but a silt trap can help your soakaway system last much longer by trapping debris and preventing blockages from forming in your crate and pipes. It needs a bit of maintenance in the form of emptying it occasionally, but compared to installing a whole new system, it’s worth it in the long run!

Installing Your Soakaway

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It’s pretty simple installing a soakaway drainage system, but you’ll need to make sure before you start that the size and type you’re using works with the amount roof area or standing water you need to control – you don’t want to install an entire system only to find that the rain overwhelms it anyway or that it doesn’t work as the soil conditions weren’t correct. You’ll need to make sure that you have enough crates to match the rainfall, that the soil type is under consideration, and that you know the capacity of the crates you’ve bought before you get them.

Here’s a quick run through the basic steps of soakaway installation:

  1. Dig out a pit in the ground for your crates to sit in
  2. Dig out a trench for your drainage pipes (usually 110mm) that will bring the water into the crates
  3. Lay out the membrane at the bottom of the crates, leaving enough for the sides and top to be covered by it
  4. Remove part of the membrane for the pipe to fit tightly inside
  5. Fill out the sides of the soakaway with shingles

Additionally, if you’re using a silt trap, you can fit that after you’ve placed the membrane inside the crates. Ensure that you’ve installed everything correctly, as if not, you could face problems like blockages down the line (if you’re worried about doing the job right, you can always get someone trained in to do it instead).

Soakaway Maintenance

The main maintenance problem you’ll have to worry about with any soakaway system is blockages – but there are other problems that you can’t always fix! For instance, if a pipe has a hole or has been punctured by a tree root, you’ll need to completely replace it (or get someone else to).

Unblocking a Soakaway

Unfortunately, unblocking a soakaway isn’t something you can do unless you’re a trained professional. If your system is filled with silt and debris, a high pressure water jet can be used to dislodge them, but this isn’t always successful, and you may still need to replace part or all of the system. This is why Silt Traps are definitely recommended, especially for the larger systems.

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