National Standards For Sustainable Drainage Systems - Understanding The SuDS Hierarchy

In order to effectively manage surface water run off in-line with the National standards for sustainable drainage systems (2025), the SuDS hierarchy must be followed. 

The SuDS hierarchy can be found below: 

Rainwater re-use is listed as a top priority and should be implemented where possible in the form of water butts/tanks. 

Once rainwater re-use has been implemented, a soakaway must be considered prior to discharging to the water course or local sewer. 

In order to determine whether a soakaway is possible, the infiltration rate must be determined.

The infiltration rate for the surface water soakaway must be established by means of an infiltration test carried out in accordance to BRE365. 

The service for his can be found here: https://www.freeflush.co.uk/products/soakaway-test-bre-365?_pos=2&_sid=620f64975&_ss=

This test will inform which route the detailed design takes. If the infiltration rate is suitable, an infiltration solution will be proposed. 

If the infiltration rate is too low, a direct to sewer solution will be proposed. 

Once purchased, we would provide the details required to carry out the test. 

Once the results are available, these should then be sent through to ourselves and we will calculate the infiltration rate and incorporate the results into the detailed design. 

Should the soakaway fail, the next step would be to discharge to surface water or combined sewer via an attenuation tank and flow control chamber. 

Our SuDS design services can be found here.