we don`t HAVE to have water softerner in place...this is optional in order to prolong the life of the membrane.
Flushing a 4040 is exactly the same...turn the tap on and allow a full flow of water through the RO for 10-15 minutes and its done.
The main reason for a 4040 is quicker production of water.
I get 400 litres in 4 hours.
Saying that, mine came with the set up I purchased...looking at the price of one new...I would think twice!!