i use a shurflo backpack, cant say anything about the wcw one, but am sure it will last the whole day like mine, and yes spares are available for most backpacks, i clean a lot of 5-6 bedroom houses, and each one will use at least one full tank, 1 and 2 bedroom houses you can get about 2 out of a backpack. the shurflo has a water controler on it, where as the wcw has not, meaning it is running at full power using more water, i have 30ft of 5mm tubing with my backpack, and it can go round the side of houses,