Potable vs Black Tank Flush Connections

[Cate&Rob]

Hi Mark (@boyscout)

The vacuum break is a high mounted valve in the black tank flush line. As long as there is water pressure (during flushing), it remains closed. When the water pressure is released, the vacuum break opens to atmosphere allowing air in so that the water in the flush line drains in two directions. Half of this fresh water continues on into the black tank and half comes back out the pressure line connection point. The flush line is now dry and cannot become a siphon action or water path for bacteria out of the black tank.

If a hose is left connected to the black tank flush, it is possible that the vacuum break remains closed and there is a water path for bacteria from the black tank back to the T connection to the potable water line. Bacteria can migrate through stagnate water in a connected flush hose.

A back flow preventer at the campground spigot is protecting the campground water supply from a siphon action through a hose left connected to an RV black tank if the park loses water pressure. It is not doing anything for the downstream hoses or connections. The inlet connection to the RV water system has a check valve that stops the supply hose from drawing water out of the RV system if the campground loses water pressure.

Rob

[Onebadhawk]

This is one of the most common misunderstandings in any campground. I can’t count the number of campers I have seen with two hoses. One going to the potable water connection and the other going to the black flush. T’d together at the campground spigot as if distance from the camper were some sort of protection.

Not disconnecting the black tank flush prevents the vacuum break from doing its job since this holds a column of water from the hose to the black tank. Then, these folks turn off the campground spigot. Now, their black tank is connected to their potable water intake.

There should only be one hose from the spigot to the camper. Connect it to either the potable connection or the (drained) black tank flush, but it can never be connected to both. The important part of this is that the black tank vacuum break must be allowed to drain (by removing the hose connection) for it to do its job and completely disconnect the black tank from anything else.

Rob

Thank you,
Thank you.
I was not aware of this.
This helps and makes the dump process a bit easier..
I'm going to get hose quick connect fittings right away..
That's a great idea too..

Teddy

[TheLexx]

I have a question. I have an orange hose for the black tank flush and a blue one for the fresh potable water. I never connect both at one time. I do my backflush at the end of our stay after I've disconnected the blue fresh water hose.

But while I of course disconnect the orange backflush hose from the campground when I'm done, I don't disconnect it from the Nautilus panel for convenience sake. Is the simple act of disconnecting that hose from the campground enough for that vacuum break to open and allow for the water column to drain in both directions?

[buencaminomark]

Hi Jeff,

This is exactly what I do. Only one hose and I know that the hose end, the potable water connection and the black tank flush connection have all never been contaminated.

I use quick connects, so the hose from the spigot is always pressurized. The key to this is allowing the black tank flush to drain back after flushing. This is clean water dropping back from the vacuum break valve which is well above the black tank. The other side of the vacuum break valve drops that water into the black tank. Thus, the black tank flush line remains dry and not contaminated.

I do use a short extension hose on the black tank flush connection so that when I disconnect the feed hose, the back flow from the vacuum break lands on the ground outside my water panel area.

Rob

My wife and are one-year newbies with one of the smaller fifth-wheels (a Reflection 273MK). As I was working out in my mind how I might implement your "one hose" set up I realized it might not work for those of us who from time to time empty our tanks at a dump station that supplies only non-potable water for rinsing tanks and hoses. Am I seeing this correctly?

Thanks,
Mark

[Cate&Rob]

My wife and are one-year newbies with one of the smaller fifth-wheels (a Reflection 273MK). As I was working out in my mind how I might implement your "one hose" set up I realized it might not work for those of us who from time to time empty our tanks at a dump station that supplies only non-potable water for rinsing tanks and hoses. Am I seeing this correctly?

Thanks,
Mark

Hi Mark,

This could present a problem no matter how you do it, if you are switching back and forth between non-potable water at a dump station and potable water at a FHU site for flushing your black tank. Even if you use a dedicated "dump station hose" you still have potential contamination at the trailer flush connection the next time your use (or Y to) your potable water hose.

I would suggest deciding on one or the other (depending on your primary style of camping) and either always flush the black tank with a dedicated hose for use at a dump station non-potable connection . . . or only use the black tank flush when you have a potable water source.

We choose the latter, since we very seldom have to use a dump station and if we do, I use their non-potable water hose to rinse the sewer hoses, but leave black tank flushing until the next FHU site.

Rob

[JColeman]

@Cate&Rob - did you find quick connects that remain pressurized like air lines? Link pls?

So I keep thinking about how all it takes is one careless or ignorant camper in the RV park ahead of you to contaminate the hose bib. I often see a dedicated black tank flush hose kept in the same container as the elbow or other black water items. This will cause cross contamination issues that I assume will carry over to the hose bib. I use sani-wipes on the outside and inside of the hose bib but I can see how that would not be enough. Your thoughts? Am I being too paranoid regardless of a one or two hose strategy?

[Chiefblueman]

@Cate&Rob - did you find quick connects that remain pressurized like air lines? Link pls?

So I keep thinking about how all it takes is one careless or ignorant camper in the RV park ahead of you to contaminate the hose bib. I often see a dedicated black tank flush hose kept in the same container as the elbow or other black water items. This will cause cross contamination issues that I assume that will carry over to the hose bib. I use sani-wipes on the outside and inside of the hose bib but I can see how that would not be enough. Your thoughts? Am I being too paranoid regardless of a one or two hose strategy?

I carry a spray bottle with a bleach solution in it. I usually give the bib a spritz then let it sit while I go about my business. I hook up the water last.

[Cate&Rob]

@Cate&Rob - did you find quick connects that remain pressurized like air lines? Link pls?

So I keep thinking about how all it takes is one careless or ignorant camper in the RV park ahead of you to contaminate the hose bib. I often see a dedicated black tank flush hose kept in the same container as the elbow or other black water items. This will cause cross contamination issues that I assume will carry over to the hose bib. I use sani-wipes on the outside and inside of the hose bib but I can see how that would not be enough. Your thoughts? Am I being too paranoid regardless of a one or two hose strategy?

Hi Jeff,

I use Gardena brand hose quick connects. https://www.gardena.com/ca-en/produc...hose-fittings/ Not very common in the US stores, but very common in Canada. I have tried the other brands of brass quick-connects, but find the Gardena plastic ones to be more durable. All the manufacturers make quick connects that are open flow and also ones that stop flow when disconnected.

Regarding "being too paranoid" . . . A lot depends on whether you drink the water coming through your RV system. Either tank or campground. We never do. When we are on the move, we won't even cook with campground water, since there is no way to know the quality of that "potable" water. As you note, you also have no idea what hose or what flush system might have been connected to that spigot before you got there. I am amazed at the number of campgrounds that don't have back flow preventers on the spigots. Most are just a faucet. There is no way to know what might have been pushed back into that system from the campsite you are on, or any other one.

We have an onboard "water quality test system". (I have mentioned this before ) When we get to a new campground, I put down a bowl of water directly from the spigot, for Molly and Angel (border collies in my avatar) If they will drink it, it is reasonably safe. If they won't touch it (and often they won't), we don't even hook up to water unless absolutely necessary.

Rob

[DaveMatthewsBand]

We spray everything down with Lysol before and after hooking up.


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[JColeman]

I carry a spray bottle with a bleach solution in it. I usually give the bib a spritz then let it sit while I go about my business. I hook up the water last.

I was just looking into that as a simple and cost effective answer. Unfortunately the bleach only lasts ~24 hours in water so I would have to remix and refill the spray bottle for the beginning of each trip. Not that big a deal but one extra thing I'd have to remember to do.

Spray Lysol makes some sense to me as DMB suggested.