By passed Black Tank Flush back flow preventer

It doesn't have to cost $50 for the cheap plastic one ..go to Lowes Under $19 for a brass one, of course you'll need two 1/2" nipples. The system should function as designed without the horrible adverse effect inside your fresh water system.

You couldn’t pay me enough to remove a backflow preventer in a spot like that.

It’s illegal for a reason, because it’s potentially a deadly accident waiting to happen.

How much liability are you willing to assume for omitting a $20 part?

When you all come down with gastroenteritis (or worse) you'll spend more than $50 not counting your lost time. That backflow preventer is not there for cosmetic reasons.

I would never use that without that back flow device!!!

So you are willing to risk SERIOUSLY contaminating the RV parks water system??? These parks have lines break all the time and guess what that creates a pull on your water line potentially sucking SH!T into the parks water system.

Since you now know the serious risk YOU have created are YOU going to step up and replace your vacuum breaker with a new functioning unit????????

It is really hard to fix stupid.

I think the risk of not having a backflow preventer is being overstated.

A couple of years ago I had a question about my black tank flush system and called the company that made it. The owner and designer of the system happened to answer the phone (small company). Among other questions, I happened to ask him about all the failures I was reading about on this forum. He said his model had very few failures, but if mine failed, I should call and he would send me a replacement for free.

He also said that he believed a backflow preventer was completely unnecessary as long as the supply line rose at least 2-feet above the tank before dropping back down to the hose connection. He said there was no way a siphon could form with 2-feet of air above the tank. If mine should fail, he recommended that I just bypass it. (He included a backflow preventer in the kit because RV manufacturers wouldn't buy it otherwise.)

You can take this for whatever you think it's worth, but at least try not to beat up the OP so hard.

We don't know how far the OP's lash-up is above the waste tank.

What he obviously does not know is that a real backflow preventer is more than just a check valve. When pressure is not present in the inlet or is at the outlet (either case) the device opens a 2" air gap between the supply and the service.

But it will be safe for the community as long as he never attaches the system to the water supply and/or overfills the black tank.

Matt

This is probably the worst idea I have ever read about on this forum (and that's saying something).

While remotely possible for a backflow to happen, the likelyhood of such an event is very very low. Would take a set of highly unlikely conditions for it to happen. As long as there is water pressure at the park faucet, it simply can not happen. If the shutoff valve to the flush connection was closed it can not happen. You could only get backflow if park water pressure were lost while you were in the process of flushing resulting in that loss pulling a vacuum on the water line. Even then the flush head would not be submerged in the black tank water and at most there could possibly be a bit of black water on the flush head. And then only if you had not yet actually run any water thru that head.

Having said that, many of us have removed those failure prone anti siphon valves, but have added an external anti siphon valve to the outside flush connection to maintain the integrity of the system.