Coopers Pet Bottles

[Brewtus]

How much of this do you need to sanitise a fermenter/cube and bottles for a 23ish L brew? I'm starting to think 25-30L of water every time is a bit wasteful.

I use about 2l to wash and rinse the fermenter, with the tap in pieces in about 3 times and then spay it with iodine solution and leave for a few minutes then quick rinse and I'm done.