Sea Ray

I would never put potable antifreeze in a fresh water holdingbtank. You will never get rid of the odor. Instead empty tank...attach 120psi air compressor to the STERN fresh water input nozzle connection. OPEN ALL FAUCETS and apply air pressure. This will eliminate all water from all lines.

The air compressor sounds like a nice plan, except possibly for the fresh water pump / check valve and the lines feeding from that to the first valve, plus all the hot water lines that would not be cleared of water.

The potable antifreeze was used by me on my boat for a half dozen years w/o any odor issue.

Here is the fresh water diagram for my boat. Compressed air would have to overcome the pump's check valve to displace water from those parts and lines.

The hot water tank retains less than a gallon, so blowing air through the hot water lines won't be as effective as the cold water lines.

http://i101.photobucket.com/albums/m52/wingless-pics/Boat/Fresh%20Water%20Supply.png

You would remove cold water line from pump, drain hit water heater then blow compressed air through the system after opening all faucets. Takes about 20 minutes....

My vessel is a 1988 415 Searay which I have owned for 10 years here is what I do; pump out your holding tank, run your fresh water tank (all faucets fully open) until virtually no water flows with pump on. Shut down pump, remove tank water supply hose from pump. Attach a 6 ft hose to the water supply side of the pump and insert opposite end into your non-toxic anti freeze jug. Before turning on pump, by pass your hot water tank supply hoses and drain your hot water tank. (the hot water tank does not need antifreeze if it is fully drained) Now turn on your pump, using the antifreeze. Run until air is out of lines, the liquid through the faucets is pure pink, then turn faucets off. You can now flush your toilets several times, ensuring you can see plenty of antifreeze flushing through to your hold tank. Once completed, shut off breaker to pump, open faucets to relieve pressure and reinstall tank water supply line to pump. There is no need to add antifreeze to your fresh water tank using this method. I know some people blow air pressure through their water system however this system has always worked well for me with no issues. (Incidentally, I winterize my engines, generator and AC system using the same method)

We've owned several boats with all kinds of fresh water accessories. All I've ever done was pump out the holding tank, drain the fresh water system completely, drain and bypass the hot water heater (there are DIY bypass kits) then run the potable pink AF through the system by opening one faucet at a time until I saw pink. Dumped another 1/2 gallon into the head and flushed it. In the spring I ran the system dry then filled the tank with fresh water and ran it dry again. Never had any problems of remaining odors or taste from the AF. A dock mate did the same process but used cheap vodka in the fresh water tank and system. He only used the pink stuff in the head.
BTW, a salty old marine mechanic taught me a way to save a few bucks on engine winterization. He said to never use the pink AF for engine winterization because it provides no corrosion resistance and may ever promote it. He taught me to use the environmentally safe auto AF (Sierra or similar) mixed 50/50 with windshield washer fluid. Did that on all the boats, too, and never had a problem in the spring. Risers and manifolds lasted 10 years (Chesapeake Bay).

Oh, Wingless mentioned rainwater getting into the bilge being an issue. One year we had an unusually heavy and deep snow. The weight split the shrinkwrap on our 32' express, dumping a bunch of snow into the cockpit. When it melted it left a foot of water in the bilge. I learned then to always pull the plug in the bilge during winter lay-up.