I just moved into a 25 year old house, and the previous owner said he never serviced the septic tankfor the 10 years he was living there. “Never needed it” he said. My street has sewer. A septic tank jobber told me to leave it alone until it quits, and hook up to the sewer. He said if you service an old septic tank, it may fail right away. On top of that, I can’t find the tank. But that’s another story. Regardless, I’m consulting a plumber, but I just wanted some additional thoughts. No more than 3 people have ever lived in the house at one time, and usually 2.