Black Tank Says FULL When It's Not And It Isn't From Dirty Sensors

[dano50]

We have a 40-gallon black tank and we have occasionally had sensor issues, but this seems much different than the usual problem. The tank acts like it has shrunk in size. We had the tank professionally pressure washed thinking there must be a ton of build-up in the tank for it to get full so quick. It turned out the tanks were already relatively clean. I decided to use a meter on the hose to fill it and measure how much water it was actually holding. It registers 1/3 full with 8.5 gallons added, 2/3 with 15 gallons, Full with 20 gallons added, and with 24 gallons added, the red light on the VacuFlush indicator in the bathroom came on (indicating the flushing system is disabled). I stopped filling at this point because I didn't want to risk running water through the VacuFlush pump the wrong way. One other thing we've noticed was that the first time we could get 1 or 2 flushes after the tank showed it was full. After we dumped, we could get 3 or 4 more flushes the second time. The third time after we dumped, we could get 6-8 flushes between the time the tank showed full and the red light on the VacuFlush came on and disabled the flushing system.

We are suspecting it is something having to do with the black tank sensors and the VacuFlush generator shut down relay sensors (red light in the bathroom) and/or some of the wiring, but we are not sure where to begin looking at that.

Anyone have any ideas?

[Gary RVRoamer]

Do you also have a gravity flush toilet in another bathroom? How is it acting?


It would take one heck of a "poop pyramid" to cut capacity by 15+ gallons, so it seems almost sure it is a sensor problem. I've attached a link to the Vacuflush installation manual so you can review how it determines the tank is full. It does NOT seem to rely on the coach tank sensors.


https://www.leesan.com/uploaded_file...structions.pdf

[Redapple]

Are you sure it is 40 gallon capacity? As previously stated reduction in capacity by 50% seems a bit out of range. Just my 2 cents.

[dano50]

Originally Posted by Redapple

Are you sure it is 40 gallon capacity? As previously stated reduction in capacity by 50% seems a bit out of range. Just my 2 cents.

We bought it new and 40 gallon capacity is what the brochure advertised. I have never had a reason to doubt that. We have lived in it full time for 4+ years and have a pretty good idea of how long we can go between dumps and when we are having sensor issues. It is showing full and the VacuFlush disables flushing capability much faster (4-5 days vs 7-14 days) than it ever has before and there are just two of us.

[dano50]

Originally Posted by Gary RVRoamer

Do you also have a gravity flush toilet in another bathroom? How is it acting?


It would take one heck of a "poop pyramid" to cut capacity by 15+ gallons, so it seems almost sure it is a sensor problem. I've attached a link to the Vacuflush installation manual so you can review how it determines the tank is full. It does NOT seem to rely on the coach tank sensors.


https://www.leesan.com/uploaded_file...structions.pdf

Both of the toilets are VacuFlush and share the same pump/holding tank.

Thank you for the link. It was informative.

[LETMGROW]

Originally Posted by Gary RVRoamer

Do you also have a gravity flush toilet in another bathroom? How is it acting?


It would take one heck of a "poop pyramid" to cut capacity by 15+ gallons, so it seems almost sure it is a sensor problem. I've attached a link to the Vacuflush installation manual so you can review how it determines the tank is full. It does NOT seem to rely on the coach tank sensors.


https://www.leesan.com/uploaded_file...structions.pdf

It would take one heck of a poop pyramid but that is definitely what it sounds like.
Op, how often do you fill and drain your tanks?
Lynn

[dano50]

Originally Posted by LETMGROW

It would take one heck of a poop pyramid but that is definitely what it sounds like.
Op, how often do you fill and drain your tanks?
Lynn

Living in the rig full-time, we have been dumping our tanks pretty much every 7-14 days for 4+ years. Normally we need to dump because the gray tank (60 gallons) gets full first. We don't remember ever having to dump because the black tank was full first or after only 4 or 5 days.

[LETMGROW]

I would try filling the black tank with water and dumping it several times to see if the capacity changes. An interval of 7-10 days might allow solids to become stuck together and form a build up.
You are full time. Are you staying in one spot or do you move on occasion?
Lynn

[450Donn]

Go buy one of those 6 foot bore scopes that is powered by a smart phone. Open the toilet and with the water turned off stick the camera down and look at the tank. Like others have said I would bet on a poo pile. No guesses that way

[dano50]

Originally Posted by LETMGROW

I would try filling the black tank with water and dumping it several times to see if the capacity changes. An interval of 7-10 days might allow solids to become stuck together and form a build up.
You are full time. Are you staying in one spot or do you move on occasion?
Lynn

This has been going on for about 2 weeks. We have dumped 3 times during that time. We have filled it with Dawn and detergent water and went for an hour long drive and came back and dumped. We have filled it with clean water 4 other times and drained it. The water always comes out clean. This is all besides the professional power washing that was done 2 days ago. The water came out almost clean then. We do a good job of rinsing every time we dump, so a large build up was really unlikely, but we had it power washed anyway. Prior to that we had it power washed a year ago. That was the first time we had done it since it was new 3+ years prior and then it was only to get the sensors cleaned and working properly. They did not find a build up then and the sensors have worked well since then.

We are not stationary. We move around frequently. We are currently at an E/W only space with a dump station available and plan to be here until this stay-at-home order is over. Closing up everything to dump every 5 days is just getting old.

[dano50]

Originally Posted by 450Donn

Go buy one of those 6 foot bore scopes that is powered by a smart phone. Open the toilet and with the water turned off stick the camera down and look at the tank. Like others have said I would bet on a poo pile. No guesses that way

With a VacuFlush there is no access to view the tank through the toilet. We have a probing camera that we might try using at the tank exit after we dump and throughly clean it next time. Thanks for the suggestion.

[jarata]

They never work right try ice in toilet and drive around

[dano50]

Originally Posted by jarata

They never work right try ice in toilet and drive around

HA HA NOT a good idea with a VacuFlush! If we put ice cubes in our toilet, we would have A LOT more problems than we do now!

[LETMGROW]

Besides the "Ice trick" is a waste of time and money. It doesn't work.
Lynn