Originally Posted by acadianbob
Two things there. Not sure if the air pressure actually goes through your pump. And there's not much room in that pump. Also, you never put AF in the fresh tank. You use a valve and hose on your pump inlet to switch between the fresh water tank and a tube where you can suck AF out of the bottles. AF in the fresh water tank is a mistake.
RV Water pumps are positive displacement, which means that it will pump any fluid (including air) that it can suck into it. You can actually purge a PD pump just by running it dry. The air from your air compressor only helps.
My Winnebago's prior owner obviously did not know to NOT put A/F into the freshwater tank. It was awful. After 5 full tank flushes, with bleach to sanitize, it was marginally drinkable. If you ever put up with that, you would see why I shy away from ANY A/F in my freshwater system.
The purge method works just as good as any other, costs nothing, and is quick and easy. Not saying anyone has to take my word for it, but it is what works for me.