Originally Posted by youroo
Flush port Below Black Tank is NOT the proper location! Check valve failure means Sewage flowing out of the garden hose port! Port Must be higher than the Black Tank!
The Next person using that fresh Water supply is wanting Safe Water not Contaminated!
And where do you think the garden hose connection to the RV is? It's below the level of the "Flush port" connection - all you've got is a solid hose connection all the way from the park's garden hose bib, through the garden hose, through the flush port (which is simply a gasketed hose connection), through the manual shut-off valve, to the back flow preventer (The thing everyone's incorrectly referring to as a check valve, and which has to be above the highest part of the black tank), then on to the black tank. To contaminate the park water system, you would have to have the black water drain closed, completely fill the black tank until the flush nozzle within the tank is completely submerged, the back flow preventer would have to fail, you would have to leave the garden hose attached to the park bib, and the manual valve at the flush port connection would have to be left open. Highly unlikely. Locating the flush port connector below the tank makes no difference.
If you want to protect the park's fresh water supply, you should use a back-flow preventer on the park end of your black water flush hose.
And what keeps us from contaminating the park water system if we attach one of those back-flushing gate valve attachments at our drain outlet??? Without a back-flow preventer at the park bib, you're still in a position to contaminate the park supply.
It should be standard practice for the park to have backflow preventers at the hose bib, but I've only seen it at one park.
I believe plumbing codes now require this backflow prevention on all outside hose connections.