Black Tank Inlet Water Connection too much backpressure with only 17 gallons of water

[clintcarter1999]

I have a 2021 Momentum 381 m-r

The primary black and grey tanks flush and I see waste contents.
I run the black tank inlet water, and I can hear it spraying the inside of the black tank.
I run the water into the black tank with Black Tank level pulled and constantly see water that eventually runs clear.

Problem 1: However, the sensors still show 1/4 tank of waste after completely dumping.

I decided to use the RV Sensor Cleaning solution, which requires that you flush and fill the tank completely.
The problem is that after dumping the black tank and cleaning until it's clear...I then try to fill it up with the Black Tank Lever Closed. I can only fill it with about 16-17 Gallons of water before there is tremendous pressure and water is spewing back out of the quick connect on the blank tank hose fitting on the Nautilus system. Water is not coming out of the toilet or other plumbing fixtures.

Question for Problem 1: Any idea why I am unable to fill the primary black tank before I have this blowback pressure at the Nautilus system? Thoughts? Ideas?


Problem 2: I was able to fill the 2nd black tank completely and yet the system shows the second black tank as empty. So I am doing a sensor cleaning solution there as well.


Question for Problem 2: Any idea why the LCD Monitor always shows the tank as empty? Could it be a fuse or perhaps the tank needs to get registered with the LCD? Thoughts? Ideas?

[Country Campers]

The tank sensors are well know to never be accurate. They usually read correctly the very first use then after that they seem to be less accurate. There are methods and solutions to put in the tank to keep them clean or get them clean but I have not heard of one that actually works and allows the sensors to work all of the time. Even our fresh tank sensors are not that accurate. The best method that I have found is to start the black tank or tanks with 10 gallons of water in them before use. Dump when needed but replenish with the 10 gallon starter, even while traveling. This will keep sediment from forming and the sloshing while traveling should keep debris from the sensors. We have also started, last year, to use the Kleen Tank solution, this has kept the odors down and has provided better clean outs when dumping and flushing, tank sensors are still not accurate and we do not depend on them.

Getting back pressure on the black tank flush at only 17 gallons is a tough one. The only thing I can think is maybe the flush nozzle is too low in the tank, that would take a scope or dropping the underbelly to see where it is at, not worth it I think. I have not tried to fill our black tank the whole way full with the tank flush line, I usually only do about 10 gallons or so but would think 17 should be ok.

Welcome to the Forum and hopefully this will help you and others will be along with their thoughts.

Brian

[clintcarter1999]

Thanks for the reply. I'll start traveling with 10 gallons in the tank. It makes sense that the water will slosh around and loosen up debris on the tank wall while traveling - I certainly fill that way on some of these roads! ;-)

[howson]

clintcarter1999

I suspect there's the dreaded "poo pile" (a buildup of paper and waste) in your black tank. Not an unusual problem as many don't realize that a good amount of water is needed to prevent the issue. There are a multitude of videos on YouTube on different hacks to break it up.

Ignore the sensors as Brian said...they'll just drive you crazy with their inaccuracy.

Howard