Upon arrival there was a water mitigation company on site. There was no active leaking, the water to the house was on. The customer brought me to the water closet in the master bathroom. The water to it was turned off at the shutoff. I checked for any visible damages or issues. During the inspection of the WC I turned on the water to it. The tank filled with water and I flushed it several times. On a couple of occasions the flapper would not make a complete seal and would run. I flushed over a dozen times and the bowl cleared every time. While discussing with the customer it was relaid to me that earlier the bowl did clog. They had to plunge to clear. They stated it cleared and they had to leave in a hurry with it filling. With this information I can guess that the soft blockage did not completely clear. The flapper was not sealing the flush tube and the water continued to run. The water spilled over the bowl and contents through the house.