Foaming root killers are a type of chemical treatment used to eliminate roots that have infiltrated sewer lines. These treatments come in a foam form that can be easily applied through the sewer line.The foam contains a herbicide that kills roots upon contact. Once the foam is applied, it expands and fills the entire sewer pipe, allowing the herbicide to come into contact with any roots that may be present. The foam also helps to clear any blockages caused by the roots.