Get some Vaseline and rub it liberally on the main gasket that goes around the lid. This will likely solve the issue.I picked up a pre-owned HW-302 off of craigslist last week. I was initially really pleased b/c it was really clean, well-cared for, gaskets & o-rings were soft... and it came CHEAP!
BUT, as soon as I got it set up and pumping water, it started leaking at the latches. I did a lot of reading & YouTube watching and realized this is a fairly common leak for these canisters. I just can't figure out how to fix it! I assumed that the water was overflowing from the quick release valves and ending up inside the lid, so I checked (and replaced) the o-rings on the quick-release valve stems, even added some plumbers tape. That connection is SNUG now. But something is still leaking! The screws holding the lid together are super tight and I haven't been able to open it up to see what's going on inside.
When I empty all the tubing and start it fresh, it doesn't leak until the water gets to the output line. I'm at a loss and don't know what else to try! Has anyone else solved this?