: I went on vacation. I shut off the water supply before I left. When I returned the toilet overflowed. The water was clean. I have three toilets in the house one down and two up. The toilet in my master bath was the one that overflowed the most. The second one upstairs only have a small amount of water on the floor. The one down stairs had not overflowed at all. I am on a septic tank. Can you please tell me how this could have happened. This is the second time this has happend. I have never had this happen while I am home.
You're a little ambiguous. "When I returned the toilet overflowed." Did the toilet overflow after you got home or did you come home and discover that the toilet had overflowed in your absence?
This is, however, a mystery. It is hard to think of anything that would cause your toilets to overflow and nothing else.
There is also the possibility that your water may not have been completely shut down. Older gate valves rarely shut down the water flow 100%. However, I cannot see how this could have contributed to the the overflow problem. The toilet bowl needs to be receiving water (bad flapper or flush valve that does not shut off) AND be plugged to overflow on their own.