They are made from a different plastic to the "standard" off the peg tanks we use. nowhere near as strong, when you try to ratchet strap it the shape will distort and may even crack.
IF YOU CANT AFFORD A PROPER TANK YET YOU WOULD BE BETTER OFF USING A LOAD OF 25L DRUMS (INSTEAD OF RAIN BUTT OPTION) AND JUST DROP PICK UP PIPE IN AND SWITCH WHEN EMPTY.IT WILL STILL BE MUCH BETTER THAN TROLLY OR BACKPACK IMO.