Q&A: Cleaning Pump Parts?
How bad is it if I don't clean my pump's parts between sessions? My boss is pretty strict about 15-minute breaks and I don't think I'll have time.
Your pump parts definitely need to be cleaned after each time you pump. Breast milk has lots of protective qualities, but it is still important to take precautions to keep it bacteria-free. Even if you don't have water nearby, you can purchase breast pump cleaning wipes (like these from Medela) to sanitize your pump parts.
If you simply can't make it work, consider getting your hands on an extra set or two of pumping equipment. You could use each set once during the day, and wash all of the parts once work has ended. (Remember to bring everything home at least once a week to wash it in hot water — a dishwasher works great.)