This info is all very helpful! Thanks so much!!
As this is new to me, please forgive some elementary questions… The previous boat owner shared with me that the best way to empty the holding tank is to have it pumped out at the marina while there getting gas. Once the system is up and running, and has been used, that makes perfect sense. But before the system has been used and is still winterized (like mine is now) do I fill the water system using the hose at the marina, run everything and flush everything, and then ask them to pump out the holding tank? Then once that's done, fill the fresh water system with the marina hose and treat the water as described above? Is there a simple way to do all of this myself without taking the boat to a marina or service center?
And then when it's time to winterize again next fall, should I go to a marina, have them pump out the holding tank and then pour the RV antifreeze into the system at the water fill spout? Also pour into the sinks and into the toilet and then run the system until there's RV antifreeze in the holding tank? What, continue until there’s a couple of gallons of antifreeze in the holding tank? Leave there until opening the next year?
Again, thanks to everyone. This is a very helpful resource!