Unfortunately I have to add some water because I live in a semi arid climate at 3500 ft (~ 1200 m) above sea level, only so my humidity is above 15% but below 30% . If you want you can measure your air cells or weigh eggs to gauge moisture loss over the course of incubation. It's all regional, for sure!
very good point . air humidity is not a same every where ,so we must check first .
for me I don t need to add any water to reach 40/45% humidity inside the bator . I always monitor the room humidity .
chooks man