Just about a week ago, I cleaned my pipe and my bong, what I did was just get a plastic ziplock bag for each, and pour in 91% alcohol, and a couple sprinkles of salt, and shake it around for 30 secs, and then let them sit for about 10 minutes, and make sure they are being soaked in the alcohol. After the 10 minutes have passed, take them to a sink and get the water very warm, but not so hot it burns you, and rinse your pieces. The tar and everything else you pipe has collected will come off like nothing.
It worked great for me, hopefully it will for you too!