Do I have to use sand or pea gravel for bedding when installing my septic or cistern tank? Posted on April 21, 2016 by Mark Peabody Yes. This is important for two reasons; It helps in the ease of leveling the tank and even inter-rib support during installation and insures that no sharp rocks or other objects puncture the tank during installation. Mark Peabody Can I use my septic or cistern tank above ground? Do I have to fill the tank with water during burial?