You can make a water purifier by using charcoal and sand. Start off with a bucket and poke some small holes in the bottom of it. Next, layer the bottom of the bucket with grass. After, dump a bit of sand into the bucket which will be used to clean the water of charcoal but be mainly stopped by the grass from falling into the drinking bucket. Next, dump in the charcoal which will begin the process of cleaning the water. Lastly, place a bucket underneath the purifier and pore the water on top of the charcoal. Any sand that does happen to pass through should fall to the bottom of the drinking bucket and isn't harmful.