Soakaway Crates

Soakaway crates, also known as attenuation crates, can be used for attenuation or soakaway purposes in commercial and domestic projects. Installing a soakaway crate system can help to control the level of surface water, especially in areas prone to flooding or heavy rains. You can combine soakaway crates with a waterproof geotextile and pipework to create an attenuation system capable of redirecting the water collected to a local body of water or into storm drains at a more acceptable flow rate. This will reduce the risk of flooding as you can install a filter to control the flow of water.

You can also use this range of rainwater soakaway crates to create a soakaway system. Wrapping the soakaway crates in a permeable geotextile will allow water to slowly leak out into the surrounding earth at a rate that the ground can accept. Thanks to this slow release the ground will cope with all of the surface and rainwater without causing any floods or stagnant surface water.

How many soakaway crates do I need?

You can combine soakaway drainage crates to make a system that’s as big as you need. Soakaway crates are modular so you can stack them on top of each other as well as next to each other. Most crates have a void ratio of over 90% so minimal space underground is wasted on the actual structure of the crates themselves. Each soakaway crate is a different size so you’ll need a different amount depending on which brand you buy. Polypipe Polystorm soakaway crates, for example, offers 5 crates per m3 but DYKA Rainbox 3S offers 3.3 crates per m3.

Soakaway Crate Sizes

The size of an overall soakaway system depends on the space you have available, the soil type of the ground and the expected flow rate of surface water. On average you need 3 soakaway crates per m3 but this varies depending on the brand and the model of the crate. Some models of soakaway crate, such as Polypipe Polystorm soakaway crates, are smaller for small projects and for more convenient transport. Transporting 20 small crates may be more beneficial than transporting 10 larger crates, given their dimensions and the fact that most crates are collapsible. Work out how many soakaway crates you need of our most popular brands here

Why use soakaway crates instead of rubble?

There are a number of benefits to using soakaway crates instead of the more traditional method of using rubble.


Traditionally, soakaways were created by simply digging a hole where the drainage pipe ends and filling it with rubble. This is quite a time-consuming process, as the transportation of large amounts of rubble is required, as well as digging the large hole and lifting the rubble to and from the vehicle. Plastic soakaway crates on the other hand are incredibly lightweight, making lifting and moving easy and quick. Additionally, plastic soakaway crates generally come flat-packed, meaning transportation is also quick and easy. The soakaway crates simply consist of a few pieces of plastic that easily clip together.

Long-term solution

Traditional rubble methods of soakaways are also a relatively short-term solution, as well as time-consuming. Over time, sediment gets washed into the soakaway along with the surface run-off, and builds up amongst the rubble, filling the spaces that the water should filter through. This results in blockages and recreates the original problem of standing water. On the other hand, plastic soakaway crates provide a longer-term solution to standing water. Soakaway crates have been manufactured with a design that doesn't get blocked up with sediment - there are a number of different pathways the water can take in order to reach the ground and infiltrate, meaning that even if sediment does pass through the grating, it is unlikely to block up the spaces - and even if it does, there are plenty of alternative pathways the water can take.

Sturdy and durable

Soakaway crates are incredibly sturdy and durable. There are a number of different soakaway crates available, depending on the area in which it is to be used - for example, if it is an area that experiences heavy traffic or lorry loading. This means that when used in the appropriate area, the soakaway crate will withstand weight above it, and will not become compressed over time, reducing the functionality of the soakaway crate. Comparatively, traditional rubble soakaways are less effective in this regard - if heavy loads are placed on them the rubble can be compressed, reducing the amount of space there is for water to pass through, reducing their effectiveness.

Before installation

Soil percolation test

Before creating a soakaway, we'd recommend carrying out a soil percolation test. This is a test to determine the absorption ability of the soil, and whether water will pass through. This can be done by yourself if you're confident in doing so, or you can ask a professional to come and take the soil percolation test.

Check the area for pipes and cables

Before beginning the installation process, you must also check that the area you are considering for installation has no underground drainage or cables running through - this includes electricity cables, gas mains, water mains, drainage pipes and street lighting cables. If you accidentally cut through or damage any of these, it can cause dangerous and potentially costly issues.

Planning and regulations

When planning a soakaway, if it is part of the work being undertaken on a new-build or extension, it must be marked on the plans. Soakaways should be a minimum of 5 metres away from the property or road, or more if the ground slopes towards the property.

Preparing for installation

The first step in preparing for the installation of your soakaway is to excavate the area for a soakaway crate and a trench in which the drainage pipe will sit. When calculating the size of the area that needs excavating, remember to allow extra width, length and depth for a base, side and backfill. Additionally, if it is under an area of traffic, such as a driveway, it will need to be deeper than if it is in an untouched area. After the area has been excavated, remove any large pieces of stone, tree roots or other debris, before laying gravel across the bottom. This will help to level out the surface and provide a surface on which the soakaway crates can sit.

During installation

Wrap soakaway crates in geotextile membrane

For best results, we'd recommend wrapping soakaway crates in geotextile membrane during the installation process - lay the membrane down before putting soakaway crates in, then wrap the membrane around the sides and over the top. Make sure you tape it down tightly to keep it secure. This will prevent any debris from entering the soakaway crates - debris and soil particles can build up over time and block the pathways of water. Stopping this will help to ensure the soakaway remains efficient and functioning.

Fit a silt trap

If you're looking for maximum efficiency and a long lifespan, you can choose to fit a silt trap on the drainage pipe that leads to the soakaway. A silt trap will prevent debris and silt from building up within the drainpipe, which can lead to blockages, flooding and damage. This will need emptying periodically, but can dramatically increase the lifespan and reduce potential blockages in your soakaway system.

Find the pipe entry point

Some soakaway crates have a cut-out, in which the drainage pipe sits, whilst others do not. Always check to see if your soakaway crate does have a pipe entry point - it might be a perforated cut out that just needs popping out. If your soakaway crate does have a pipe entry point, mark it on the membrane before cutting the membrane and folding it around the pipe. If you are working with several soakaway crates, ensure that any other pipe entry points on the other crates face inwards. If your soakaway crate does not have a pipe entry point, the pipe should be pushed right up to the soakaway wall.

Back and side fill

Once the soakaway crates are in place, back and side fill is required to ensure the structure remains stable and in position. To do so, we'd recommend using a sand or shingle material. As well as the back and side fill, a layer is also required on top of the soakaway crate, before the hole can be re-covered with soil and any other finishing products. If the soakaway is in an area that experiences some traffic, it is recommended to increase the amount of soil required on top - this will increase sturdiness and prevent and ground movement.

Read further advice here on how to avoid a blocked soakaway or click here to find out how many soakaway crates you need

Do you need help with your order? Call our experts on 01752 692 221 or use the live chat on your screen and we'll be happy to assist you.

Products in Soakaway Crates:

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