What is Dust & Vermin Proofing we hear you ask?
It’s a type of foam that is sandwiched between tank and roof to prevent pest and contaminant entry via small spaces and gaps. It prevents mice and other small animals contaminating your most valuable resource … water. We recommend using Dust & Vermin Proofing on all residential tanks … or where water will be consumed by humans 
https://youtu.be/5vQeByZIFrY