Last year after replacing the fuel filter I also had to clean out the drain line as it was corroded clogged. When I put it back together, I was sure to send the drain hose to ground (I could blow air through the hose and it came out the hole in the top of tank under the cap). Now, though, the tank builds up pressure. It never did this before, and I think the hoses were switched from when I bought it as I always marked them when I changed a filter. SO, the question is, is there a diagram of the hoses on the charcoal filter so I can check that they are correct? I think either the charcoal filter is clogged, or hoses are not correct on it causing the pressure buildup. Is there any reason or issue with running the vent hose to the ground as well as the drain? Any other suggestions?