The capsules didn't work for me either
I had some fun recently soldering 3/4" ball valves into my main supply lines so I can isolate part of my house easily. I tried those vitamin E like capsule thingies and they didn't work well for me at all. I saw them in a book, and I'm an engineer, so it seemed cool. Problem was, the capsule itself seemed too big around to fit into the pipe (yes, I know there are two sizes...) and by the time I got it in there, it had ruptured and was useless. I think you're supposed to warm the capsule a bunch in your hand and sort of compress it.
I solved my problem by holding the pipe down for a while to drain a bunch of water, and then raising it up so the water couldn't go "uphill" easily. Oh, and swearing a lot seemed to help too. ;-) Next project I'll try bread.