Good idea if it is.
It is a good idea; my house, garden, and where I can park is all on a gradient (looks beautiful in the Winter, having my very own mini ski slope in the back garden), but since the tank I've been kindly given is 400 litres, I may have to give it a quick fill when I drop Wor Lass off (she won't work past 2 or 3 pm otherwise her nose starts to bleed, and she threatens me with having to do housework, and then my nose starts to bleed), so I will get a transfer pump anyway, so I can fill up quickly if I need to.
I really don't know how much water we'll use though, till we start working together, and looking at my work it'll vary quite considerably from the type of work we'll be doing.