I tried their calcium reactor as well and it leaked too. I was able to get the media reactor to stop leaking by building up a silicone barrier. It's ugly but I'm not one of those sump dwelling admirers. It's the only size that works for me so I had to make it work. I decided to run GFO so bought a second. It does not leak. I ditched the GFO in favor of NoPox so trashed the rigged reactor and have been running the one that worked out of the box since. You have to make sure your hose clamps are super tight. You need to use the ones that are threaded and use a wrench because you can't get it tight enough with a screwdriver. 1 out of 3 worked for me out of the box. I recommend using a different brand but if this is the only size that works for you than make sure it's returnable.