Actually it's not perfectly normal in the strictest sense of the word as indigenous peoples generally have a bowel movement within a couple of hours of eating and have a comparatively empty bowel most of the time, whereas it's all the crap we eat that stays in our systems and causes this "back up" if you like.
My wife's family suffer from HNPCC ( an heriditary form of bowel cancer) so she regularly has to have colonoscopies which prior to she drinks something to empty her bowels. Afterwards, once her bowels are totally empty, she can, if she eats correctly, replicate this more natural process of digestion as long as she avoids processed foods etc, so the consultant that told her about it is obviously perfectly correct.
Your bowels do well being as empty as possible, as our lack of excercise and bad diet and this build up you speak of is a major cause of non-hereditary colon cancers as well. Drink loads of water and follow Champagne's advice.