Abstract: A modular backflow prevention system for a sprinkler system includes a first fixed union end piece attached to a first end of a fixed water inlet pipe through a first union mating adapter where a second end of the fixed water inlet pipe is in fluid communication with a water supply. A fixed union end piece with seal is attached to a first end of a fixed water outlet pipe where a second end of the fixed water outlet pipe is in fluid communication with the sprinkler system. A removably backflow prevention assembly is removably attached to the first end of the fixed water inlet pipe and the first end of the fixed water outlet pipe by removably attaching a second union mating adapter to a second union end of an inline ball valve and removably attaching a third union mating adapter to the fixed union end piece with seal.