If a real estate agent sells you a house with a material defect and doesn't tell you about it, are they liable?

In this situation, the owner of the house was away for a full year, leaving the home for the real estate agent to sell. The significant repair need was not listed by the owner. They may not have known about it when they wrote up the contract with the realtor to sell the house. The problem may have developed during the year the home was up for sale. But the new owners moved in and suddenly, had a very expensive bill to pay for this repair (plumbing). Since the real estate agent had access to and control over the property for the year it was up for sale, were they liable to monitor the property for developing repair needs? Are they in any way liable for selling a defective house to an unsuspecting buyer without telling them what repairs were needed? I'm looking for responses from those who have specific knowledge in this field, particularly those knowing the rules and regulations that realtors are expected to follow as a condition for holding a real estate license. This was in the state of Texas. A home inspection was done but the defect did not materialize until the toilet had been flushed several times, not just once, as the inspector had done. This was not my purchase or sale. It happened to a business associate / friend.