In being prepared, there's a saying: "three is two; two is one and one is none." It means that for the REALLY important things, like food, clean water, light and fire you need backups. You also need backups to your back-ups. For water, that may mean having several sources: rain barrel, pond, well, neighbor's pool. Great sources, but would you want to drink it without some process to clean the water? Sure, chlorine will disinfect it (usually), but it may still look and taste scummy. That's where filtration can be very useful.
I read about this filter and then bought one. It works like the expensive filter set-ups from a company that starts with a "B" but costs about 10% of the price --or less. If you can supply the 2 food-grade buckets, you can have a water filter that gets out the nasty stuff for about $35 including shipping. This website seems to be the least expensive for the same product I bought -- a set that includes the filter and spigot. The site also has assembly instructions. I bought from a different company and paid $10 too much. Got too excited and bought before I finished my research. DUMB.
This site also has the pre-made systems that include the buckets for under $50, so you don't need to buy or scrounge them.