Hong Kong tap water is conforms to the World Health Organisation’s recommended guidelines for drinking-water quality. Check these links from the Hong Kong government: 1, 2, 3.
The tap water itself is perfectly safe. However, the pipes to your building might be old and degrade the quality of the water. If you live in a modern building, you probably do not need to do anything. If you live in an older building, the quality of pipes and holding tanks may be poor.
Many options are available: boiling water for 20 minutes or less; filtering it; using spring/mineral water, etc. It's the choice of yourself.