Actuallly... FHA et al are pretty strict about this. You need to locate the leach field and tank approximately, distance to well, etc. It is no different than reporting zoning, etc. You need to ID if the Septic is surfacing. Caveat the rest away. Pulling the lid on the well tells you what the measured flow is unless a really old well. Ask how deep and how much flow. If they don't know state "The owner did not know."
I appraised a church and there was a huge area of leach field that was surfacing behind the church. I flagged it and replacing that leach field is a $20,000 plus project.