Using storage containers for water changes.

I have recently bought a couple of storage containers (Handy Crate brand) and have no recycling number on them so I am unaware of what they are made of. I contacted the manufacturers and they are unaware of its exact make up which baffles me but anyway. Do you think I should use something else? If so what do you use? I am planing to use large containers to fill up near the tap and mix in water conditioners and salts and then pump 13 metres to the tanks.

I actually ended up returning the containers and bought a 100litre HDPE water tank. I read that High density polyethylene is food safe and shouldn't ever leach any chemicals into the water.