My son made a small water filter using, From bottom to top, 2" layer of large gravel, 2" layer of Small pea gravel, 2" layer of activated Charcoal for aquarium filter, and the top is a 6 " layer of sand, all place inside a 1 gallon Iced Tea jar that has a flow valve in the bottom. After cleaning everything thoroughly we ran water through it until the water coming out was completely clear. He's afraid to drink the water now until he has it tested. Any advice? Does it have to sit for a while until the microbes build up in the sand? or Is it ready to go immediately? We are on well water so the water going in is already good to drink, but do pollutants in the sand or gravel pose a safety concern? I don't want to dampen his spirit because, I like that he did it on his own, but, I don't know either?