When to tell (possible) employer that you breastfeed?

My son will be 7 months old on Monday. He is EBF. I've been a SAHM since I was put on bed rest last September. Now I'm looking for a job and I was wondering when you are supposed to tell them you need to pump. Should I mention it before or after I'm offered the position? Would they consider it a hassle and not hire me if I told them ahead of time?

I'm hoping to get a part time job and also one in town so my in laws could even possibly bring him to me to nurse while I'm on break. He's only nursing ever 4-5 hours or so. Friday he went 5.5 hours and was fine.