Straight from the site
Different drum versions give different flow characteristics.
Version 1 - has outlets running sequentially, (ie) 1, 2, 3 , 4, repeated.
Version 2 - will give a delayed sequence (ie) 1 & 2, 2 & 3, 3 & 4, 4 & 1, repeated.
Version 3 - has them opposed (ie) 1 & 3, 4 & 2, repeated. (Our best selling version)
Version 4 - Designed for use with our Revolutions units. Water is sent to 3 outlets at the same time.