Though it may seem strange, this problem isn’t all that uncommon. Inside the walls of your home, your tub, toilet, sink and shower are all connected to the same water supply pipes. A problem with one faucet can be related to pipes leading to another part of the bathroom. Each is connected to the main water line in the same way.
If your faucet leaks when the toilet is flushed, then the bathroom faucet drip is most likely caused by high water pressure. The water pressure in the main water supply line has probably exceeded 80 psi, causing complications. When your toilet is flushed, water flows from the supply line to refill the tank. But, if the water pressure is too high, it can force water through a seat washer that may be worn, cut or deteriorated, causing your faucet to drip. However, if your water pressure is 80 psi, you should have your pressure reducing valve evaluated by a plumber to see why the house’s water pressure is so high.
Once the pressure ceases, so does the leak. However, over time, this problem can cause more complications.