I'll assume you're doing enemas because a doctor ordered it. If not, then I recommend you just don't do it at all. Enemas are not harmless and unless there's constipation they have no benefits. And even then they shouldn't be used routinely. There are safer, healthier ways to manage constipation.
I'll also assume you're sure you're using the device correctly, that it doesn't have some sort of valve that is blocking flow.
That said, it sounds like you're simply not inserting it far enough. The tip needs to go 2-3 inches into the rectum to get past the anal sphincter. One inch isn't enough. You need to use some lubricant on the tip, preferably something water-based. Your local pharmacy should have a number of choices. But in a pinch you can use stuff like Vaseline, or even a plain vegetable oil such as olive oil.
Although this article is written as instructions for nurses giving enemas to patients, it covers things you need to know about enemas.