Question: how much does it cost to install a residential septic system?
Answer: A three- or four-bedroom house typically requires a 1,000-gallon septic tank, and the cost for the tank and installation averages between $8,000 and $15,000. For a house with five or more bedrooms, you'll most likely want a 1,500-gallon tank, and that will cost $15,000 to $25,000.