We were over in Mandurah yesterday picking up a couple of water tanks to put on Hubby's car.
He was looking at getting a 100 litre tank to go under the tray on his Cruiser but I pointed out that he could get 2 86 litre tanks for less than the price of the bigger one so that's what he did.
One will be for drinking and cooking and the other will be used for showers, cleaning. dishes etc. I think having 2 will also be better as if one gets a hole or leaks then we will still have water.
Maybe 160 litres of water is a bit of an overkill but hey, he won't be able to use the excuse of not enough water to shower so I think that benefit alone makes it worthwhile.
Another benefit...We wont have to take the 20 litre water containers so will have more room in the tray.