The answer to 'why is my irrigation system brown patches' is that brown patches in your lawn are often caused by issues with your irrigation system. Common causes include underwatering, overwatering, clogged or broken sprinkler heads, and improper sprinkler coverage.
Underwatering can cause the grass to dry out and turn brown, while overwatering can lead to fungal growth and other problems. Clogged or broken sprinkler heads can result in uneven water distribution, leaving some areas too dry and others too wet. Improper sprinkler coverage can also lead to brown patches where the grass isn't getting enough water.