If You Raise The Septic Lid How Far Should The Sludge Water Be Up In The Tank?

It can be as high as the bottom of the cover if it has rained alot or you haven't had it pumped in a while. It is normal. What you don't want is the solids (crap, toilet paper, hair) to be at the top as they may plug the pipes going to the leach field or get into the leach field and plug the holes in the pipes. If that happens be prepared to shell out $10,000 for a new leach field. Pump it every two years. Don't put anything that isn't septic safe in your septic and lose the garbage disposal. NO FOOD down the drains.