Basic guidance for the construction industry about when to use a flocculant, what type of flocculant to use and how much of it to use, and advice on managing costs and risks when using flocculants on a construction site. Flocculants are a type of commonly used chemicals that have a wide range of applications in everything from food processing to wastewater treatment. Flocculation refers to the process whereby fine particles are made to clump together into a larger and heavier particle called a ‘floc’. This process is very useful for separating solids from liquids across different industries. Flocculants are used in the construction industry during temporary works, where they are used to create ‘flocs’ from very fine particles, such as clays in water. Creating heavier particles makes the clays easier to settle out of suspension and capture on site. This can play an important role in preventing silt pollution from entering streams and rivers from construction sites.