I had a situation where the main shut off would not shut off. I called the city and they came out and shut off the water supply to the house. The main shut off used a rubber washer that had broken up. The guy who came out told me to go and get a gate valve of the same size as the original. He came back and installed it for me. Days later I noticed that the water meter was not turning. Called the city again and they came out and replaced the meter. Turns out the broken washer in the old shut off was caught up in the old meter.