A disc filter is a type of water filtration system, and a plastic disc filter is a type of disc filter where the filtration discs are made of plastic material. They generally have a series of grooved rings, forming a cylindrical filter with each groove crossing the other in different directions, creating a three-dimensional matrix of pathways, using these pathways in the plastic discs to trap particles and impurities as water passes through them. Different grades of filtering are achieved by varying the size of the grooves (usually specified by a particular disc colour), thereby representing an equivalent grade of filter mesh (table 1). Plastic disc filters are often preferred in certain applications due to their resistance to corrosion and their lightweight nature. They are commonly used in agricultural irrigation systems, wastewater treatment plants, and industrial processes.
| Colour | Purple | Green | Red | Orange | Blue | Grey |
| Mesh | 40 | 80 | 120 | 150 | 300 | 800 |
| Micron (µ) | 400 | 200 | 130 | 100 | 50 | 20 |
Table 1: An example of disc filter filtration grades.