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Open Roads Forum  >  Fifth-Wheels

 > Black tank flush overfill

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nickthehunter

Southgate, MI

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Posted: 06/22/22 06:42pm Link  |  Quote  |  Print  |  Notify Moderator

way2roll wrote:

nickthehunter wrote:

Why do people not leave their black tank valve open when flushing the tank? Valve open, tank won't overfill, why would I want to risk a disaster?


Because it's not only the force of the water from the flush to "wash" debris from the sides of the tank, it's the physics involved to use a 1/2 or 3/4 full tank's rush of water to flush all that debris out the hose. I repeat this process several times until I get clear water. The trick, as the op found out, is not to walk away and let it overfill. It's only a disaster if that happens.
since I’m not going to be storing drinking water in it, it just doesn’t need to be that clean. I find as needlessly wasting water making your poop holding tank OCD clean, and rude to needlessly hold up everyone in line behind you at the dump station as you refill and refill and refill and refill again until you get clear water. I’ve seen it personally way to many times.
A 5 gallon pail of water down the commode right after dumping works just fine for me.

* This post was edited 06/22/22 07:04pm by nickthehunter *

Cummins12V98

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Posted: 06/22/22 07:48pm Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

Cummins12V98 wrote:

dougrainer wrote:

OK, one thing that can happen when you do this, it can BREAK the 3 inch down tube from the black tank. The Pressure involved when you do this is tremendous. 45 psi or more has filled the black tank and now the tank has expanded(swollen) and popped either the 3 inch down tube loose or the 1.5 inch vent tube loose. We know this because instead of water coming out the roof vent and overflowing on the roof it came out the bottom from the top of the tank. Because the tank broke open at the tank which is a good thing instead of out the roof vent. NOW, if you do NOT fix the problem on top the tank, you will have black tank odor migrating into the lower bottom cavity because it is NOT sealed now. The RVIA standard for both Gray and Black is to hold water when overfilled. With Black we fill until the water is just below the toilet ball valve and on Gray with water coming into the shower or tub. Also, unless you access and clean out the top of the tank and the underbelly and insulation, you will now have a musty smell all the time. Both inside and out. Doug


How do you know this? There is a roof vent there for a reason, I don't see how pressure can be added when there is a vent.


I suggest you start a Black flush and let it go with valves closed. If the pipes to the tank are glued, you will have sewage water coming out the roof top vent. I HAVE NEVER DONE IT! I have FIXED quite a few that customers have done it. AND, if the 1.5 inch pipe is NOT sealed where it comes thru the outer roof deck, you will get water into the roof cavity. With water coming out from the interior ceiling panels and such. Doug


I think I said exactly all that. How do you know the tank can build pressure??? I don't see how if there is a vent pipe.


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Cummins12V98

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Posted: 06/22/22 07:50pm Link  |  Quote  |  Print  |  Notify Moderator

nickthehunter wrote:

way2roll wrote:

nickthehunter wrote:

Why do people not leave their black tank valve open when flushing the tank? Valve open, tank won't overfill, why would I want to risk a disaster?


Because it's not only the force of the water from the flush to "wash" debris from the sides of the tank, it's the physics involved to use a 1/2 or 3/4 full tank's rush of water to flush all that debris out the hose. I repeat this process several times until I get clear water. The trick, as the op found out, is not to walk away and let it overfill. It's only a disaster if that happens.
since I’m not going to be storing drinking water in it, it just doesn’t need to be that clean. I find as needlessly wasting water making your poop holding tank OCD clean, and rude to needlessly hold up everyone in line behind you at the dump station as you refill and refill and refill and refill again until you get clear water. I’ve seen it personally way to many times.
A 5 gallon pail of water down the commode right after dumping works just fine for me.


Are you a weekend warrior or full timer??? If Warrior do what you want and let the next guy deal with the CHITZ. Full time you want to keep it clean as possible as it all can add up.

sprintnut

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Posted: 06/22/22 09:09pm Link  |  Quote  |  Print  |  Notify Moderator

nickthehunter wrote:

Why do people not leave their black tank valve open when flushing the tank? Valve open, tank won't overfill, why would I want to risk a disaster?

Nick, I close the black valve when using flusher because the flusher does not clean the tank out. After years of use I have found filling the tank several times and draining does a much better job of getting stuff out. Maybe the shape of my tank is difficult to rinse with just the flusher but I do what works best for me. By the way, my accident was a error on my part by hooking water hose to flusher instead of water supply fitting.


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sprintnut

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Posted: 06/22/22 09:31pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

Step away like a boss. Nothing happened.

What does this mean?

Johnny G1

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Posted: 06/22/22 10:14pm Link  |  Quote  |  Print  |  Notify Moderator

And driving down the road for a few miles and the stuff in the tank will be easier to clean the tank, not much sticking in the tank when on the move and then dump and flush, save a lot of water and don't hold people up, Just my thought's after 50 some yrs of camping and travel.


98 Mountain Aire 34' 210 Cummins Puller and 2001 dodge dully with all the toy's, 400 + hp pullin a 2001 32.5' Okanogan 5th wheel, new to us after 5 yrs with the 28' Travel Aire. Lots of fun.

dougrainer

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Posted: 06/23/22 06:24am Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:


I think I said exactly all that. How do you know the tank can build pressure??? I don't see how if there is a vent pipe.


Once the water starts the climb up the vent pipe, the tank WILL expand and that combined with the PSI of the input water and the force required to push it up that 10 foot of pipe will add pressure. Not much, but will add pressure. Doug

* This post was edited 06/23/22 07:19am by an administrator/moderator *

Cummins12V98

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Posted: 06/23/22 07:45am Link  |  Quote  |  Print  |  Notify Moderator

Earlier it was a totally different story. "The pressure is tremendous" ONLY if completely restricted and it is NOT with a vent pipe.

You said: OK, one thing that can happen when you do this, it can BREAK the 3 inch down tube from the black tank. The Pressure involved when you do this is tremendous. 45 psi or more has filled the black tank and now the tank has expanded(swollen) and popped either the 3 inch down tube loose or the 1.5 inch vent tube loose.

Remember tanks are designed to be FULL of POOP.

* This post was edited 06/24/22 07:36am by an administrator/moderator *

StirCrazy

Kamloops, BC, Canada

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Posted: 06/23/22 07:47am Link  |  Quote  |  Print  |  Notify Moderator

sprintnut wrote:

nickthehunter wrote:

Why do people not leave their black tank valve open when flushing the tank? Valve open, tank won't overfill, why would I want to risk a disaster?

Nick, I close the black valve when using flusher because the flusher does not clean the tank out. After years of use I have found filling the tank several times and draining does a much better job of getting stuff out. Maybe the shape of my tank is difficult to rinse with just the flusher but I do what works best for me. By the way, my accident was a error on my part by hooking water hose to flusher instead of water supply fitting.


I also close mine, but the first time I timed how long it took to get to 1/2 a tank with strong water pressure and I never let it go over that time. the tank doesnt need to be full to get it clean, 1/3 of a tank or more will do it, you just have to do it a few times.


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PButler96

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Posted: 06/23/22 10:34am Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

The RVIA standard
Now that's funny.

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