Question: Why does my bathroom faucet drip when I flush the toilet?
Answer: If your faucet drips when the toilet is flushed, you probably have high water pressure. What's happening is the water pressure in the main water supply has gone over 80 psi, forcing water through an old seat washer whenever the toilet is flushed and water flows from the supply line to refill the toilet tank. This is possible because all the water in your bathroom plumbing is connected.
High water pressure can cause washers, fittings, and other plumbing to wear down sooner than usual. It can also affect appliances. Learn more about high water pressure (how to spot it and what to do about it).