When we flush the toilet in the MB there is a loud knocking noise. We were able to alleviate the noise if we turned on the hot water faucet forcefully just before flushing for several months. Now the hot water pipe is knocking, also. How do we alleviate this horrible noise, please?

Did the knock happen right when the toilet tank was finished filling and the fill valve closed?

[B]The toilet knocking occurs as the water goes down the hole and at the very beginning of the filling of the tank. The sink knocks when both are going at the same time.[B]