If you have existing drainage problems after rainfall (easily identified by waterlogged areas) then the construction of a soakaway or an alternative means of drainage is essential! Soakaways don’t work in heavy clay soils because the water collected in the soakaway can’t filter out into the surrounding ground. You can test the ground or ask your local Building Control, they will know your soil type and be able to advise and If the ground is not suitable, you still have other options. Collecting and storing water then pumping it to another area of your garden where you need it is a great idea, or discharging into a sewer, again if a soakaway won’t work in your location your Local Building Control Department will be able to confirm your best option.

You will need to carry out a percolation test:

First dig a small square hole 300mm x 300mm at the depth of invert (this is where your drainage pipe will feed into the soakaway crate)

Fill the hole with water and leave it to soak overnight, come back and check it next morning.

Now refill the hole, watch and time how long the water takes to seep away from the 75% point to the 25% point (this is 150mm), then calculate as follows.

http://www.pavingexpert.com/drain08.html

This should be done in a few areas across your proposed driveway or adjacent lawn area then take an average from the readings.

A soakaway must be at least 5 metres from the house and 2.5 metres from your neighbours’ fence. The pipe flowing to the soakaway should be 100mm underground waste ideally, but the Building Inspector may settle for 75mm, and it should be laid to a fall of 1:40. Soakaways need to have a firm base especially if they are under vehicular traffic, if possible its always easier to construct a soakaway under a lawn or pedestrian area to reduce the amount of work required.

This depends on the ground conditions around the soakaway crate. A very general rule of thumb is; 1 cubic metre (1 m3) for a 50m2 drive and 2 cubic metres (2m3.) for a 100m2 drive (or 50m drive with a steep gradient) and always remember to allow for you roof area if you are discharging both into the same soakaway. Either way for your soakaway to work properly it has to be able to discharge the incoming water quicker than it fills up.

there a number of ways to calculate the size of soakaway required… The most commonly used in the industry is:
Soakaway Volume = Area x (Rainfall Rate/3000)
For a standard 60m2 roof or driveway in the UK the calculation would be:
60m2 x (50mm/3000) = 1m3 volume
This means you would require 5 of our CORE Water Crates to create a 1m3 soakaway. In other words, 1 crate should be used for every 10-12m2 of area to be drained.

As a general rule of thumb for a driveway of around 100m2 is, the bottom of a soakaway should be at least 1.5m down this will allow the pipe to fall toward the soakaway at a 1:40 fall and reach the top of the crate. Leaving maximum clear space below the invert level (the level that the pipe enters into the top of the soakaway) in this case 1m. This will give the soakaway a good volume to collect water in and more chance to slowly infiltrate that water back into the surrounding soil, if the pipe enters lower down the soakaway you will not get full use of the void created by the soakaway crate, as the ground  surrounding the soakaway crate begins to become saturated the pipe will begin to back fill and water is therefore more likely to stay on the surface.

For larger surface areas the depth to the bottom of the hole could be as much as 2.5m or consider more shallow soakaways at various locations.

This depends on the type of surface you choose, impermeable non porous surfaces such as concrete or macadam will cause more run off, which will need to drain into your soakaway where as porous surfaces such as Resin Bound or Gravel Stabilisers will drain across their entire area, allowing water back into the ground at source feeding the thousands of tiny aquifers that in turn feed into larger water courses and form a vital part of natures food chain, sustaining micro organisms necessary to keep natures,  natural balance in place.