There are plenty of reasons why a toilet could be constantly running. If no other solution or replacement works, then one possibility is that your toilet is running due to high water pressure. High water pressure is a problem you’ll want to deal with immediately, as it can cause leakage and even more serious issues. High water pressure can cause non-insulated or loose pipes to hammer against the wall or against other pipes, causing potential internal damage or bursts.
The cause of high water pressure depends on where you get your water. Unless you use your own water well, you probably get your water from a local city municipality, which operates public utilities and water districts. If your water pressure is high, then it may be a problem on the water utility provider’s end. You may want to contact the water company to express your concerns. They may offer to check the water pressure coming into your home and they may even install a water pressure reducing valve to dial down the pressure for you. However, in some instances, they may explain that it’s your responsibility to deal with the high water pressure on your own. If so, you can hire a licensed, professional plumber to do the same thing.
It’s always wise to call a professional when you suspect that high water pressure is your issue. They’ll be able to confirm this for sure by putting a gauge on one of your faucets to test your home’s water pressure. They’ll also review further options with you.