Legal Question in Real Estate Law in California

If you had no reason to know about the septic system, then the seller failed to disclose a material element of the condition of the property system and you can declare that they breached the agreement to purchase and cal the deal off or insist the terms of sale be changed.

Did the seller provide a "Real Estate Transfer Disclosure Statement" as required by Civil Code section 1102.6? The statement has a check box for "Septic Tank." Was it checked? I believe it is customary for a seller or the seller's broker to provide the buyer with some assurance that the septic system is functioning properly at the time of sale, usually by paying for a routine inspection and, if necessary, pumping. As far as "certification" goes, my understanding is that this occurs when the system is first installed or modified, not upon sale of the property, but there could be local requirements in your county.