Micro Minnie FLX Blacktank Check valve location

[EXW]

It rarely pays to discuss things like this if the other party is certain they are right! But for those who may read this later, I feel it is important to avoid thinking this is a normal check vale because they are two different things and this one involves safety of everybody who may use the water supply!
One reason these tend to fail is because they have such a small amount of pressure used to open and close them. Often just simple gravity is involved. That makes it really easy for them to fail if they get loose and tip over as the gravity doesn't pull the mechanics closed!
If we swap out the air admittance valve with a check valve we totally lose the safety factor! The person who causes the problem may be down the road to the next campground before anybody gets sick at the last campground! But that is the reason for this type valve to be required as drinking black waste, even in small amounts, can be really serious. Besides the "yuck" factor!
Human waste is about as serious as it gets for pollution we might drink!
But looking at why and how this works is not that difficult if we give it a little thought.
There's a little drawing on the side of your valve that shows the path? It shows the air can come in around the top and go toward the tubing that normally carries the fresh water we use to flush the tank.
When we go to the dump station, connect to the fresh water faucet and flush the tank, that water supply is also connected to the rest of the campground water supply! There is no special well or supply for flushing water, just a faucet that often has a label telling us not to drink from that faucet!
That label is just part of of several things the rules try to keep us safe!
The idea is that this valve is often open to let air in, but closes when we put water pressure on it. That closed valve lets the water flow past and go to flush the black tank and it should not leak in this area.
Then when we turn the faucet off and pressure is gone, this valve should move to open to let air in (air admittance valve?) That air relieves the siphon as the incoming water reverses and begins to run back out the hose where it can enter the water supply!
View attachment 1110564

Normally we close the faucet and would cut off that hazard but then what happens if things are not going "normal" the day you are there lined up to get out of the park?

If a camper that has had the wrong type valve installed is hooked up and suddenly the water supply loses pressure, the siphon from the water supply lines can suck black waste out of the tank and into the fresh water supply lines for the whole campground!
Nobody knows it, nobody tells people to stop drinking the water and people can die!
Normal operation is the blue line is fresh water coming in and the air portion is closed, so water can't leak.
The green line is when we turn off the faucet, the air route is open and siphon from water running back down the hose doesn't pull black water from you tank into your hose!

If you put a normal check valve in this spot, you have a direct connection between your hose and your black waste tank!!
Maybe you get lucky and don't get enough into the whole campground system and only get black water into your own personal hose?
I may sound a little hysterical about drinking black water but I like to think I'm not going to kill YOUR grandkids and especially not mine!
Putting in the right valve may seem like a drag but I find going to funerals are not my favorite thing either!

Appreciate your thoughts on this. Black tank items shouldn’t be treated (no pun) as just “yucky water” that’s no big deal.

For me, the BLUF is I’m glad I found this tread because this B&B Model 571 vacuum breaker component that failed and failed hard for me wouldn’t have been the first place I was going to check for a leak issue. I actually though I had a ruptured connection just inside the wall at the outside fitting or somewhere along that line.

It turns out when running a couple of tests it wasn’t just water coming from the horizontal connecting point but also above where the vacuum valve portion should open/close. The cheap plastic failed there too.

Thankfully I caught this doing PMS at home and not at some campground where, yes, this could have been a potentially bigger issue.

I ended up replacing mine with a brass version of the same design/same purpose and it now functions as designed and I feel confident about heading back out on the road.

 

[Morich]

It is one of those cases where we might look at a check valve and say that would stop flow. But then when we think about how often a check valve leaks and lets water through, it just makes more sense for the regs to specify a different valve. And the rules for separating black water from fresh are the same on RV as they are on home plumbing. It is just not supposed to be done!

Over the years, I am certain the folks who set these rules have looked at both sides of what to require.
And when it comes down to possibly killing some of the more fragile folks like kids or elderly or anybody with a weakened system, it just is not worth the minor effort/expense to put in the right valves as required.
There are just too many cases where things fail and don't work as expected for it to make sense and try to cut corners just because we may not fully understand the details of how this valve works.

If the codes don't want home irrigation systems set up that may allow ground water from irrigation to be sucked into the fresh water, I certainly don't want to risk sucking black tank water into the fresh water!

 

[ChrisRiley]

Here's a pic of the area under my bathroom sink. I'm not sure what everything is, but I have not had any problems. It's a 2024 2108 FLX.

 

[ChrisRiley]

Is there a plumbing diagram available for the Micro Minnie FLX? I would like to know what all those things are.

 

[ChrisRiley]

Here's a look of the area above the previous picture. This is directly under the bathroom sink. You can see a black line coming up from below and it's attached to some kinda device and then there is a black line going back down.

 

[ChrisRiley]

The black line going up is the black tank flush. It goes into the black tank along side a bigger black line. I have no idea what that is.