Roy Hinkley wrote:They all pretty much work the same way the difference being what happens to the first flushed water. You can easily harvest the first flush in one barrel strictly for irrigation and have the rest cleaner for other uses.
This vid shows using a 55 gal barrel as a reservoir to hold the first flushed water for later use, the rest is cleaner and diverted elsewhere. You don't need to do this if the water is for irrigation only but it does help keep sediment from clogging up your water system over the years.
https://www.youtube.com/watch?v=ch-YsD9rOGk