Holding tanks. We all have them, and occasionally we’ve got to clean them. Blackwater tanks especially can make your life miserable when the little demons of built up crud need to be removed. We’ve seen plenty of occasions at the dump station when some poor shlep has pulled in with a holding tank that just doesn’t want to “let loose,” and they’ve resorted to running a water hose in and out of their black water port, churning and stirring all that evil muck. Yuck! 
Now imagine all that evil muck showing up in your drinking hose. Not! You never use a dump station hose to fill your fresh water tank. You’re careful never to use an unknown hose to fill, right? But there’s still a way to get evil stuff in your drinking water: Backflow.
Backflow happens when a fresh water system gets “cross connected” with a source of bad water–or other contaminant. For us as RVers, it’s as simple as a garden hose left in contact with contaminated water, hooked up to the hose bib. Under the right conditions, that water can come back UP the hose, into the hose bib, and in to the fresh water lines of the house.
What are the “right conditions” that favor back flow? Let’s say you’re flushing out your holding tank. You’ve got one of those neat “Hydro Flush” systems that let you hook a garden hose to your holding tank at the same time you’ve got a dump hose hooked up. In the middle of your dump and flush operation, the local fire department cruises through your neighborhood, testing fire hydrants. They pull the caps off a nearby hydrant, crack the valve wide open, and blast water every which way. Unfortunately, this happens at the same time you’re flushing your tank, and the sudden draw down in water pressure allows your black water to pulse backwards up the garden hose and right into your house. The same thing could happen if your private water well pump system went on the blink when you’re flushing a tank.
What’s to prevent this from happening? If you bought a commercial tank cleaning system device, chances are the outfit included a simple backflow preventer to be installed between your hose bib and the garden hose. If a sudden loss of pressure were to set up a ‘perfect storm’ for a backflow, the device steps in and stops the backwards flow of fluids, protecting your household drinking water. But oddly, not everyone sees the value of a backflow preventer. Maybe they consider it a nuisance and simply ignore it.
Ignore backflow to your peril.
A mouthful of bacteria laden water can more than ruin your whole day. But blackwater isn’t the only issue. Consider the harmful affects of pesticides (from using a garden hose sprayer), or automotive antifreeze (from flushing the radiator on the old bus). Backflow preventers are cheap, easy to use, and available at pretty much any hardware store. Use them and rest easier.
Buster Backflow courtesy of American Backflow Prevention Association
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