Btw I saw a post by sunflower about suction power with her PISA. I had the same experience but yesterday I realize that it was the two flaps (that open n close as the air pumps in) giving me problem. My two flaps are slightly tear due to my washing. I changed the two flaps with the spare pair that comes with PISA and it works. Haven't seen 3 oz appeared in the milk bottle in less than 5 min for a long time. U can check if your flaps has any tear and not so tight anymore...