According to Wedmd.com, a navel piercing typically takes between 4 months and 1 year to heal completely. During this time, you should not go swimming in a public pool or use a hot tub.
Take care to follow any specific instructions your piercing technician gives you. To prevent infection, you should clean the piercing area regularly with antibacterial soap. You can also soak the area with clean salt water. If you do use a public pool before your piercing is fully healed, you risk an infection. Signs of an infection include unusual pain, swelling, or redness in the area of your piercing. Get prompt medical attention if you think your piercing might be infected.