Have a 2007 H44DS with 2 electric quietflush (fresh water) heads. Work great, no odors but on two occasions now have been unable to pump out. Most recently when vacuum attached from pumpout boat, able to suck next to nothing although tank about 2/3 full. First thought is that vent line is clogged, but if so I would expect to have problems flushing, right? I recently shot some water down the vent from the outside to see if this would fix it, but the only way I can test is to call the pumpout boat again, which is getting embarrassing. I have noticed that several hours after flushing the water level in the bowl goes down to nothing, so perhaps the tank is venting that way, but it does not smell. I have been able to discharge overboard through macerator, but most places we go cannot do this (legally). Please help me work through this logic problem. Thanks (have your book, Peggie, nice job) S/V Breathless H44DS 234