Hepco becker 2 litre canister for water?
 

Got mine 2 litre canisters with holder to my panniers today.
The idea was to use one for reserve fuel and one for water.
But now it says "for fuel only" in the instructions.
Anybody tried to use it for water?
My guess is that it is good for water but H&B dont wanna risk that people put water in the tank and drink fuel.

My guess - and it is a GUESS, not a fact - is that the markings are there to persuade people not to use them for water, and thereby risk mixing the two up and getting poisoned. I would suggest that you mark the water canister with clear paint markings and use them as you intend. Historically, military use of jerry cans relies on one can and several different colours to distinguish petrol, diesel, drinking water etc. Seems to be pretty foolproof in a military context.

Touratech has exactly same canister and it says " for oil and water"...

You can get those in 1.5 and 2 litres versions, the 2 litre one is black IIRC.
That would a be a foolproof way of having them separate.
Sorry, my mistake I was thinking of the Fuelfriend containers.

Petro-proof plastics will often not pass tests to be used in food/water applications. They leach tiny amounts of chemical which can be tasted (a good test when no one can say what a good mineral/salf level is) in water and so rejected. Put water in a petrol can for 6 months in bright sunlight and you'll probably increase your risk of getting cancer by the same as smoking half a woodbine but no one really knows, the water standards have saved many lives in their time. Drink this water every day and you might have a reason to get a lawyer, hence they mark it. I have the same issue with pumps at work, no water standard markings if even perfectly safe, microscopic bits of rubber change the taste.

Andy