We bought a boat 20 years ago that had a Whale manual bilge pump for the tank pump-out. There were a number of problems with the whole installation so I ripped it out and started from scratch. The Whale pump went on a shelf in the garage in case I ever wanted to use it. For almost 10 years I could find it in the dark it smelled so bad. Make sure to use the right pump. On that boat I used a Sealand SLT12 electric diaphram pump. I would have just as soon had a manual pump but there were space and access problems. The Sealand worked trouble-free for 10 years until we sold the boat. It used some sort of ureathane diaphram instead of neoprene or some other rubber type material. I agree with Brian about the Y-valve. That is how we did the installation described here. The only difference is that we put in a Y-valve so the heat could go directly overboard. The tank and pump out proved to be 100% reliable so we always used the tank so we could have gotten along without the direct overboard.