The responsibility to pay for septic repairs typically falls to the seller. However, repairs of any kind found at inspection are generally negotiable. Contract terms usually dictate the course of action, but sellers may have such options as doing the repairs themselves, splitting repair costs with the buyer, giving the buyer a closing credit equal to the amount of the repairs, or refusing to do anything. If an agreement on repairs isn't reached, the buyer does have the legal right to walk away from the transaction.
Don't forget about disclosure
In all states, sellers are required to disclose any known problems with a home to potential buyers. If there's a septic issue after closing that the sellers knew about, they will be liable for the entire cost of the repairs.
For that reason, it's good practice for all sellers to perform their own septic system inspection. That way, the seller is protected from any future septic issues after the closing.
For information or to make an appointment, contact Morse Engineering and Construction.