This tread is little bit old but I have one "stupid" question. I got my hw-302 today (it's my first canister filter), set it up and it works, its not "dead" silent like some of you stated but it's OK.
Now the stupid question. Do canisters leak when you lean them on side (not completely, maybe just 10-15 degrees) or shake them harder?
No it shouldn't leak at all. Try putting some lubricant on the seal. That might help.