As it has been said, it is normal. There's no person on the earth who showers and no hair comes out! 30 hairs in the shower is even a very low amount!
Everyone looses ~100 hairs a day, some people even more, but it grows back! The hair follicle cannot operate indefinitely. It must rest from time to time. When you loose hair, those follicles enter the resting phase, but at the same time, other follicles get out of the resting phase and begin growing hair, so the actual amount of hair doesn't really change.