Your child is very regular in his bathroom habits, but there is one problem with him: He insists on pooping standing up in the bathtub and refuses to sit on the potty. What can you do about this?
Standing up for a bowel movement is a common habit for children who were used to defecating in their diaper while standing. Trying to poop while sitting probably feels unnatural and uncomfortable for your child.
Start to solve this problem by persuading him to leave the bathtub, where he could stand and feel most comfortable, to the potty, where the stools belong.
Next, suggest that he sit to urinate and then continue to sit until just an instant before he needs to defecate, and reward him for his effort. Continue to encourage him this way—particularly about fifteen minutes after meals and before bedtime, when the urge to have a bowel movement is greatest—until he accidentally releases stool into the potty while sitting.
Reward him greatly for this success. Soon, your reward system and your support will ease him into correct behavior.
American Academy of Pediatrics, (2015). Bathroom Behaviors. Healthy Children [Online]. Available: https://www.healthychildren.org/English/ages-stages/toddler/toilet-training/Pages/Bathroom-Behaviors.aspx [Nov. 21, 2015]