I have 1.53 acres and on my septic system we are supposed to have 3 sprinklers in our back yard. I have on sprinkler that is broke and i need to fix it but once i fix it im afraid that since the other two are buried im pretty sure that it will break the other two. So i wa wondering how far apart are the sprinkler heads supposed to be apart?

Sprinkler heads are supposed to be installed with what is known a "head-to-head" coverage.

Sprinkler heads do not throw equal amounts of water everywhere. While the water might be falling at a rate of 2"/hour 6 feet away from the head, it might be falling at a rate of 6"/hour 10 feet away from the head (I'm making numbers up, but you get the point). So to balance these differences out, each sprinkler head should spray to the next sprinkler head so that every spot in the yard is getting hit by at least two heads.

So if you have a yard that is 30' x 45', and you are using heads that can spray out to 15', then you should have 3 rows and 4 columns of spray heads, all 15' apart from one another to create an even watering pattern.