The answer to 'why is my irrigation system brown patches' is that there are several common causes, including improper water distribution, drought stress, pest or disease issues, and nutrient deficiencies. Brown patches can be a sign that your irrigation system is not delivering water evenly across your lawn, leading to dry, stressed areas. This can be caused by clogged or damaged sprinkler heads, broken pipes, or issues with the irrigation controller.
In addition, drought stress, fungal diseases, grubs or other pests, or nutrient deficiencies in the soil can also contribute to brown, patchy areas in your lawn. It's important to diagnose the underlying cause in order to address the problem effectively.