My 2000 326 MY didn't come with one and I was informed that Carver didnt factory install these. Simple installation, you just need to splice into your vent line and install the filter canister. I purchased a Sealand Sanigard from WestMarine and installed it within 10 minutes. You could easily make your own with activated carbon (pet store), 8 inches of 1.5" PVC pipe, rubber coupling (Homedepot), and plastic fittings. See WestMarine site for picture.