Water hammer is a common problem that can occur in your home's plumbing system. It is caused by the sudden stop of water flow in the pipes, which creates a loud banging noise. Here are some steps you can take to fix water hammer:

1. Turn off the water to the clothes washer, dishwasher, or other areas that experience water hammer. The device will usually have a shutoff valve that can be turned clockwise to shut off the water. In some cases, you may find an intermediary shutoff valve farther up the line.
2. Fix waterlogged air chambers located on the hot and cold water lines ahead of each tap.
3. Reduce water pressure.
4. Install water hammer arrestors.
5. Change worn out or broken faucet check valve spring.
6. Change bad shower cartridge.
7. Secure loose water pipes.

These methods can help you fix water hammer in your home's plumbing system. You can also try turning all the taps on one by one and then turn them all off in reverse order. This can potentially release air pockets in your pipes.