How often can you pump during the workday?
The "Break Time for Nursing Mothers" law requires employers to provide time and space "each time such employee has need to express the milk." If the space is not available when you need it, your employer is not meeting the requirements of the law.
A breastfeeding mother must pump her milk as often as the baby usually eats. During the early months of your baby's life you will probably need to pump your milk every 2-3 hours during the workday.
Because a baby's feeding schedule changes over time, your pumping schedule will probably change too. Once your baby begins eating solid foods, you may be able to pump less often.