I'm a Houdini Newbie and I followed a tutorial on sand It's working how I want it. Most of the sand is falling into a cylinder and through a small hole. I'm getting a few stray particles breaking free see attached. Anyone got any ideas how I could fix this ?

Look for a SubSteps settings in the DOPNetwork node and increase it to 2 or 3. It basically tells Houdini how accurately to calculate the physics. Obviously the more steps, the longer it will take to calculate the simulation.

Thanks