These sand filters look really good, but this link shows another approach. It's similarly granulated, requiring only gravity: https://drive.google.com/file/d/1yKf1rQ718GIgx7-4mLsQhKzh9OxcSPT4/view?ts=5b02b349

Published May 22, 2018 20:36 by Anthony Reid Harvey

These sand filters look really good, but this link shows another approach. It's similarly granulated, requiring only gravity: