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dave_stream · 05-03-2021, 09:52 AM

Hi all,

My approach for flushing the black water tank has been:

- Make sure the black water dump valve is closed
- Connect the hose to black water flush inlet
- Turn on water and fill the black water tank -- watching the % go up on the monitor
- Pull the black water dump valve to empty the black water tank
- Repeat a few times.

However, I just noticed the warning notice underneath the flush inlet saying "CAUTION: Do not use the tank flush valves unless the fullway termination valve is in the open position. May result in an unsanitary condition leading to illness or personal injury." In looking at other threads mentioning this, it seems "fullway termination valve" means the black water dump valve...which I interpret to mean that I should NOT be flushing the tank the way I do it, I should instead keep the valve open the whole time.

It seems to me that wouldn't clean the tank as well. Can anyone advise on this?

Thanks,
Dave

pjshier · 05-03-2021, 10:05 AM

I have entertained similar thoughts, and generally heeded the warning sticker, with a few brief violations thinking that more liquid in the tank surely improves the possibility that more solids will be carried out of the tank.

The what-if comes down to the human condition and the capacity for distraction as the dog runs off, a fellow camper maneuvers too close or honks because you are taking too long and needs attention, one tire looks low and should be checked, etc. and before you know it you are overflowing.

If there is some other principle at work in the design of the system - I am all ears.

Vantair · 05-03-2021, 10:35 AM

We have used a hybrid approach.... of sorts successfully so far....being attentive staying at the valves.

Typically with a mostly full black tank, let that go 1st and while it’s mostly done, turn the additional fresh water hose flush on then “closing” the black tank valve for 10-15 secs then open again.

Repeating The above open/close with the fresh flushing water routine until black draining is clear. (We have a peekaboo clear section at the head end of the slinky to verify all this).

After 5-10 passes and all is clear on last few try’s, close the black valve and open the grey valve till empty.
Works so well, never had to use any enzyme or stinky deodorizing solutions these last 7years.

Lastly flush the slinky with a spray/clean attachment, stow the tools and drive.

Piggy Bank · 05-03-2021, 11:29 AM

Hi Vantair,
Thanks for posting this.
How long do you think this takes you to do?

I am curious, as we currently are Those People who only use our black tank for liquid output.

One of the reasons for this is that it is just super-quick to dump since we don't have a slurry and don't have to be concerned about clearing out solids.

For our quick weekend camping it has always seemed like more than we wanted to deal with. But your approach sounds more do-able than some.

Dennis C · 05-03-2021, 11:42 AM

Quote:

Originally Posted by dave_stream

Hi all,

My approach for flushing the black water tank has been:

- Make sure the black water dump valve is closed
- Connect the hose to black water flush inlet
- Turn on water and fill the black water tank -- watching the % go up on the monitor
- Pull the black water dump valve to empty the black water tank
- Repeat a few times.

However, I just noticed the warning notice underneath the flush inlet saying "CAUTION: Do not use the tank flush valves unless the fullway termination valve is in the open position. May result in an unsanitary condition leading to illness or personal injury." In looking at other threads mentioning this, it seems "fullway termination valve" means the black water dump valve...which I interpret to mean that I should NOT be flushing the tank the way I do it, I should instead keep the valve open the whole time.

It seems to me that wouldn't clean the tank as well. Can anyone advise on this?

Thanks,
Dave

I've been doing it the same way that you describe. This was recommended by my Airstream dealer during my orientation. How much do you typically fill your black tank with the flush hose before opening the valve? I often go to 75% or higher. I've found this to be very effective at flushing the black tank.

JunkYard · 05-03-2021, 12:00 PM

I do as above if there is no line and I’m taking the camper home. Otherwise I’m there for far too long and I’m just gunna put more in it. If you fill and flush it is amazing how much more stuff can come outta that tank. I can dump at home as well so that’s part of it.

s1000pre · 05-03-2021, 12:01 PM

I also open & close the valve as necessary to clean and highly suggest you “SET AN ALARM” on your phone. I set mine for every two minutes, then handcuff myself to the valve when I reach 70%. I have kids with constant interruptions. Last fall, things almost went horribly wrong!

Cyclist · 05-03-2021, 12:30 PM

I have read several stories and met one person who flushed the black tank with the valve closed and was distracted with very bad results. I keep the valve closed for about five minutes and carry a small kitchen countdown timer with me just in case. I usually repeat several times. On occasion I will flush with the valve open.

DCPAS · 05-03-2021, 12:47 PM

My 2019 Owners Manual says to close the black dump valve and fill the tank to about half full. The manual for the black tank flush equipment which was included in the materials in the bag says to never use the system unless the dump valve is open. The concern is the obvious one - overflowing the toilet.

I fill to about half full, but I sit in the trailer and watch the level the entire time.

Dennis C · 05-03-2021, 12:55 PM

I open the back window in my 23FB so I can watch the tank level monitor. If you push the button for the tank level two times quickly, then it will display the level for about 5 minutes. A little dot appears next to the level to show you that it’s in this mode. I’d much rather monitor it this way than time it, as some water supplies fill the tank faster than others.

LilPeanut · 05-03-2021, 01:16 PM

To be clear, the illness and personal injury is if you let it overflow into the rig. The DW will provide the personal injury. Ask me how I know.

Lesson learned. Set a timer. When it sounds, pretend the house is on fire. I flush mine without incident now but there was this one time…

panamerican · 05-03-2021, 01:34 PM

I have filled my tank to flush it out with supplied water from the toilet and I look down the hole to verify and I typically fill it up pretty good.

When using the included black tank flush, I keep it closed until about 1/4 full then open the gate empty and let it continue to rinse out for a few mins. Been using these methods for pretty close to 20 years with no ill effects.

In my mind keeping the gate closed with the tank flush on is no safer or better than filling the tank with the toilet.

Now the gray tank is another matter, I let the sinks fill that tanks and one day the lavatory sink drain plug closed by itself and I caught it just as it was overflowing the sink, but never have overflowed the black tank...yet.

dave_stream · 05-03-2021, 01:34 PM

Thanks everyone!

It sounds like everyone thinks the only risk to closing the black water valve while flushing the tank is if you accidentally leave it too long and it overflows. I can imagine that would not be fun. Based on the warning sign, I was worried there might be some other issue as well.

I have been filling it to the brink of full -- up to 94% or as soon as it hits 100% then opening the black water valve to dump it -- but it seems like maybe it's a better idea to do a little below that, maybe 88% or something just in case.

crazylev · 05-03-2021, 01:40 PM

Since our tank monitors stopped working years ago, I have the long suffering wife watch down the toilet till it gets to very close to top, she then gives a knock on window that means let er go!

I also time how long it takes to get to this point and after first time, just go by time. This will vary depending on different places and water pressure. Even if I go back to same place I always use timer for first fill. Three times if no one is waiting. one and a half if there is a line up.

Someday I will have to write about my poop explosion at dump station....twice!

JL

waninae39 · 05-03-2021, 01:43 PM

flush the black 1st
when done
flush the grey

that washes out the pipes

DO NOT leave the ext vales open when camped. the tanks should be 1/2 to full when dumped to get sufficient flow action

Dennis C · 05-03-2021, 01:48 PM

Something like this?

Peter C · 05-03-2021, 02:25 PM

We have a 27FB with 40 gallon black tank. I recently was on full hookups and decided to flush the black tank several times. I was amazed that even after flushing the tank several times (I close the valve and fill to over 50%) there were still "chunks of solids" that come out. The water is completely clear and then you see a few "items" flow though the clear elbow.

It takes a long time to fill so I have not been too concerned about using a timer. I do not multi-task while doing this as I have had friends that have over flushed. Not pretty.

Vantair · 05-04-2021, 08:08 AM

QUOTE
Hi Vantair,
Thanks for posting this.
How long do you think this takes you to do?

GREAT question. If level, imagine 5 minutes. If off level where slinky is slightly going “up hill” last took 15 minutes for the many more times of open/close/fill repeat due to gravity. That was the longest time ever but was in our own full hookup campsite when breaking down camp so no one else was harmed in the extra process.

Our logic is the fresh water spray while repeating the open and close routine has more chance to “pry” and flush stuff out.

Seems to do best with a healthy downward slinky (go figure)!

Ted S. · 05-04-2021, 09:43 AM

Close the valve for a few minutes and then dump again, you will get more out. Repeat a few times. Look at the video the guy did on YouTube, its clear you want to accumulate some water then dump again.

Pull the warning sticker off.

Mikebrady62 · 05-04-2021, 12:21 PM

Quote:

Originally Posted by Dennis C

I've been doing it the same way that you describe. This was recommended by my Airstream dealer during my orientation. How much do you typically fill your black tank with the flush hose before opening the valve? I often go to 75% or higher. I've found this to be very effective at flushing the black tank.

I do this as well. 75-90% and then let it flush.
I also like Dennis' idea of being able to double tap the display so it stays on and watch it from the outside. But as others have warned... DO NOT GET DISTRACTED. I'm guessing it's an experience no one around you would ever forget.