The number of crates you need for a soakaway system doesn't just depend on how big your roof area is; you need to calculate the whole impermeable area (roof size, patio size, driveway size etc.) as well as perform percolation tests to determine the permeability of the ground around the property.
The most important factor determining whether your property is suitable for a soakaway is space. All soakaway systems need to be at least 5 metres away from your property; if the areas surrounding your property don't span more than 5 metres you can't install one, and you must consider alternatives.
The second most important factor is the soil type - its condition and permeability - of where you would be installing the soakaway crates.
Determining your impermeable area
Your property's total impermeable area is one of the details you would need to provide to work out how many crates you need. To work this out measure the areas your property covers consisting of the external hard surfaces — such as roofs and garages down towards your patios, driveway and paths. This should give you a total impermeable area in m2.
Once you have your total impermeable area the other pieces of information you will need are percolation test results which determine the suitability of the soil in which you would place the soakaway crates.
For instance, if storm water collected within your soakaway is slow to infiltrate the surrounding ground, the soakaway size needs to increase. If storm water is quick to dissipate into the ground the soakaway size can be decreased. This is prevalent in areas with heavy clay soil where soakaways should not be utilised.
Ground porosity is found through a process called a percolation test. For more information, and instructions on how to perform a percolation test, contact JDP today.
Our advice , once you have your test results, is to get in touch with JDP's Technical Support team who assist you in calculating the soakaway size required. If possible they would also like to see a plan of the property showing where the soakaway would be located. They can also determine, depending on your test results and space availbale, whether a soakaway is the best option for you and offer you other alternatives.
Before any installation, systems should be approved by local authorities.
Technical Support: 01228 794445