Well, the good news is that the tamperproof lock doesn't really need to be reinstalled...it is a good thing for commercial operations. Is the water going over the top of the overflow valve? If it's running, it must be going somewhere! If a new valve didn't resolve your issue, the only other thing I can think of is that your house water pressure is very high - that's easy to check. In the states, the big box stores sell an adjustable Korky valve...almost the same as the Toto universal replacement, except you need to adjust the bowl/tank ratio after making a few measurments rather than setting it to the desired number on the Toto valve...they are made by the same company, and will work fine, once adjusted. The goal is to get the bowl just filled when the tank is full so you don't waste water.