By passed Black Tank Flush back flow preventer

Atlee wrote:
Didn't mean to start a firestorm, but apparently I have.

A few answers or explanations.

1) I plan on getting a black flow preventer for my hose I used when dumping the black tank.

2) It sounds like some, if not most on here, believe I keep a hose hooked between the spigot at the camp site and the black tank flush system all the time. Never the case. I hook it up when I need to flush the tank.

3) It also sounds like some if not most here think I have a full black tank when hooked up. Not so. I dump the black tank, then hook up the hose to the flush system, and turn it on. I let it spray and dump at the same time, so there is no way "stuff" from the black tank can enter into the hose.

4) There is a vertical run of at least 3 feet before the black flush piping exits the rear of the trailer. The black flush connection on the rear of the trailer is nearly 4 feet above the ground.

So are you going to install the proper back check before you sell or trade your unit?

YOU may know how to avoid a SERIOUS problem but the next guy may not and that effects ALL of us.

No, I don't plan to replace the old piece. If the dealer supplies me with a new one under warranty, I'll put it on should I sell the trailer. But at this point I do not plan on getting rid of this trailer.


For one thing, I can't trade trailers every 2-3 years like some folks do. For another thing, this trailer suits us both quite fine. At the recent RV show, I saw no floor plan that I'd even think about trading my current trailer for.

If I should sell it before it's time, I'll instruct the buyer on what he needs to do, and since I'll be getting out of the RV lifestyle when I sell it, I'll throw in the non potable water hose with the back flow preventer.

Cummins12V98 wrote:

Atlee wrote:
Didn't mean to start a firestorm, but apparently I have.

A few answers or explanations.

1) I plan on getting a black flow preventer for my hose I used when dumping the black tank.

2) It sounds like some, if not most on here, believe I keep a hose hooked between the spigot at the camp site and the black tank flush system all the time. Never the case. I hook it up when I need to flush the tank.

3) It also sounds like some if not most here think I have a full black tank when hooked up. Not so. I dump the black tank, then hook up the hose to the flush system, and turn it on. I let it spray and dump at the same time, so there is no way "stuff" from the black tank can enter into the hose.

4) There is a vertical run of at least 3 feet before the black flush piping exits the rear of the trailer. The black flush connection on the rear of the trailer is nearly 4 feet above the ground.

So are you going to install the proper back check before you sell or trade your unit?

YOU may know how to avoid a SERIOUS problem but the next guy may not and that effects ALL of us.

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

Ditto!!!

Can you and any other poster explain to me how water laced with fecal matter can flow back up the over 2.5 feet of water line, out the back of the trailer which is nearly 4 feet off the ground, back through the water hose and into the campground water system?

I understand that a vacuum on the campground water system could suck fecal laced water out of the black water tank. What I do not know is how this could happen unless the black tank sprayer is completely submerged in the fecal laced water. Is this not so?

If it is so, then why would anyone, using any common sense, hook up the water hose to the black tank flush system and open the spigot while the black tank is full? That sounds like someone who wants to over flow their toilet in the bathroom.

agesilaus wrote:
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.

That's OK. When I was a kid, I sucked on garden hoses syphoning gasoline from my dad's car to use in the lawn mowers. I have no clue how many gallons of gasoline I swallowed back then.

Too much paranoia in my opinion!

Atlee wrote:
Can you and any other poster explain to me how water laced with fecal matter can flow back up the over 2.5 feet of water line, out the back of the trailer which is nearly 4 feet off the ground, back through the water hose and into the campground water system?

I understand that a vacuum on the campground water system could suck fecal laced water out of the black water tank. What I do not know is how this could happen unless the black tank sprayer is completely submerged in the fecal laced water. Is this not so?

If it is so, then why would anyone, using any common sense, hook up the water hose to the black tank flush system and open the spigot while the black tank is full? That sounds like someone who wants to over flow their toilet in the bathroom.

agesilaus wrote:
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.

You will NOT get a 'plausible explanation' and you know it :B

Atlee wrote:
...why would anyone, using any common sense, hook up the water hose to the black tank flush system and open the spigot while the black tank is full?

If common sense was actually common, many laws, rules, and safety measures would be unnecessary...

waterboy502000 wrote:

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

Ditto!!!

Double ditto!!!

Old-Biscuit wrote:
Waste tank would need to be FULL and PRESSURIZED to florce flow from waste tank back thru Spray Nozzle, UP 2' then down into hose which would need to be connecged to a water supply system that has NO pressure in order to 'contaminate' the water supply system

Sorry, but that is plain wrong. REALLY wrong.

First, codes and regulations cover the requirement of backflow prevention devices to prevent backshiphonage of contaminated water into potable water systems. There are several types of devices that can do that and vacuum breakers are the most reliable and safest which is why they are specified. You can find vacumm breakers on places like residential sprinkler systems for example. CGs can have them on every single faucet at a site. Ordinary check valves are not an acceptable substitute.

It is possible for there to be conditions under which there is negative pressure created in a potable water system that can draw contaminated water back into the system. The water pressure within the distribution system can fall below that of the plumbing system it is supplying when high flows are pumped out of a system like when say a fire hydrant is used. Or there could be a water main break or a water main being flushed. Or a momentary pulse in the system pressure. Or a CG shutting off it's main supply could easily cause it. There are other conditions too...

It is NOT the RVIA that decides whether or not a backflow prevention device is required in an RV. It is probably covered by NFPA 1192 which is the standard that covers RV plumbing systems. I couldn't find a free copy of it online the other day when trying to find something else so can't provide a link. Backflow prevention in CGs will be covered by a plumbing code or standard or Health Agency.

Here is Minnesota's Dept. of Health requirements for "Cross Connection Control" for example that is specifically for recreational camping areas. You can find similar requirements across the US and Canada.

If someone thinks a vacuum breaker isn't needed in your RV, you should get your RV-ing licence taken away for good and be banned from owning an RV for life. :M

My vacuum breaker was installed next to my silverware drawer and above the electrical inlet. On the manufacturers website, it clearly states that the breaker may expel water and should be installed in a location where that water will not cause harm. Here is a spoon to stir your coffee.

Lynnmor wrote:
My vacuum breaker was installed next to my silverware drawer and above the electrical inlet. On the manufacturers website, it clearly states that the breaker may expel water and should be installed in a location where that water will not cause harm. Here is a spoon to stir your coffee.

Egad. If the RV industry has a chance to mess something up, they will.