How far does your septic system need to be from the property boundries in Maine?

I've put in septic tanks in many states and they are all 20' from the property line. The 20' is called an easement line. Most cities in the east let you build right up to the property line, but if you are out in the country it's the 15' line.Some states will allow you to build to within 15', but it's 20' for a septic line or tank.