Soakaway - Flow rate

[davey]

i have dug a hole 800 deep by500 wide 600 long for my soakaway i poured in 16 litres of water in and it took 3 hours to drain is this adequate i will only use it once/twice a week to wash my 12ft x 6ft pen down not sure if clay

[Bob_A]

Sorry can't answer your question myself but while you waiting for someone who can have a read of this
http://www.pavingexpert.com/drain08.html

[Tony McC]

16 litres over an area of (0.5 x 0.6) = 0.3 square metres is roughly 53 litres/m² in 3 hrs which is 18-ish litres/m² per hour.

Then you need to calculate just how much water you expect to use while washing down. Let's say you'll use 50 litres, so you need to have the capacity to hold those 50 litres which will then trickle away. So, to provide 50 litres in a traditional filled soakaway with 30% voids, you'd need a structure of at least 150-ish litres. If you use a storm crate with 95% void, then 50-60 litres would be adequate.

A typical storm crate of 500 x 400 x 1000mm = 0.2m³ (which is 200 litres) would be more then enough.