Black tank shows constant 2/3 full...

HappyCamper1 · 08-05-2021, 08:35 PM

....Just finished our inaugural trip with our 2016 Simplicity...a little curve swaying but other than that handled great! Averaged over 17 mpg for 3600 miles , down to Texas and back home to WNY. I noticed the black tank, after 4-5 dumps still shows it to be 2/3 full?? Any suggestions?? Thanks

rowiebowie · 08-05-2021, 10:35 PM

Hey, congrats on a sucessfull trip!

It would be helpful to determine if your black tank sensors are mounted internally (where they could be covered with debris) or externally (where they could be shorted or otherwise showing an incorrect reading).

I don't know if there is an adjustment or calibration that can be done, but that requires a user manual for the sensor system.

mumkin · 08-06-2021, 02:01 PM

Roadtreks have the traditional inside sensors which by RVing traditional rules will never read accurately once black tanks have been used. After a few months with my first rig in 2004, I realized that the sensors were useless and have ignored them ever since. I quickly learned by my usage when the tank needed to be dumped. And one can always take a flashlight and peer down into the depths.

Some blame it on toilet paper, but I never put it into my tanks, and the sensors still never read accurately.

Yes, there are dozens of recommended procedures involving this or that chemical, or combinations of soaps and such, ice cubes, wands, and whatever. And with a few hours of labor and driving around and repeated dumps, you can get it to read empty, but honestly I have better things to do than this wasted effort that will be undone as soon as you actually use the tank again. lol

Want a B · 08-06-2021, 02:07 PM

Fill your black tank 3/4 full of potable water. Add a healthy dose of dish washing soap. Drive around for a couple hundred miles. Any TP or other debris that's shorting the sensors should be now cleared.

I prefer Mumkin's method, "And with a few hours of labor and driving around and repeated dumps, you can get it to read empty, but honestly I have better things to do than this wasted effort that will be undone as soon as you actually use the tank again."

booster · 08-06-2021, 02:32 PM

IMO, the only real fix that works and doesn't revert back to not working right away is bite the bullet and replace the sensor system with one of the outside the tank sensor setups like Seelevel and others.

We did that many years ago and not had any misread problems since and before that is was a constant PITA to get clean and then they always stuck again when we next traveled.

JeanM · 08-12-2021, 05:12 PM

Wait a minute... Happy Camper!

AKA: the only tank chemical that provides us with any small measure of relief to the constant problem of "just dumped the tank, gauge still says full"

Overall, I'm with Mumkin.

Nspekter · 08-12-2021, 08:20 PM

I’ve had good results with the wand. Takes about 10 minutes.

JeanM · 08-12-2021, 08:57 PM

Quote:

Originally Posted by Nspekter

I’ve had good results with the wand. Takes about 10 minutes.

General caution

It's key to know what kind of toilet is in the rig before trying any of these tricks. As far as I'm aware, "the wand" isn't compatible with macerating toilets and neither is the ice-cube-trip-to-nowhere technique.

engnrsrule · 08-13-2021, 06:34 PM

I use the wand on the black tank every time. Also have not issues using paper. They hang up sometimes but wanding normally clears them. I use this in black and gray tanks. https://www.amazon.com/dp/B06XXVJFSR/

My gray tank is another story. I am going to try adding some liquid dishwashing soap (as opposed to regular dish soap) next road trip as it is supposed to be better at breaking down built up stuff.. My gray tank cannot be "wanded"

rogerstg · 08-13-2021, 10:09 PM

Quote:

Originally Posted by engnrsrule

My gray tank is another story. I am going to try adding some liquid dishwashing soap (as opposed to regular dish soap) next road trip as it is supposed to be better at breaking down built up stuff.. My gray tank cannot be "wanded"

I've had success with powdered dishwasher soap for the gray tank. The problem with regular dish soap is that it suds, a lot. I imagine bubbles would wreck havoc on those sensors.

BTW, if anyone has problems with suds from using the wrong soap, a pint of vinegar in a bit of clean water sloshed about should clear it up. Run a tank of clean water through as a final rinse.

michaelingp · 08-14-2021, 01:17 AM

How do you tell which (internal or external) sensors you have?

booster · 08-14-2021, 01:45 AM

Quote:

Originally Posted by michaelingp

How do you tell which (internal or external) sensors you have?

Internal sensors are a single pin wire connection at 3 different heights on the the tanks and the externals are usually a circuit board on the outside of the tank full height or the tank.

mumkin · 08-14-2021, 02:55 PM

Quote:

Originally Posted by michaelingp

How do you tell which (internal or external) sensors you have?

If it never reads empty after you dump, they are internal for sure. You don't even have to crawl under to look.

mumkin · 08-14-2021, 02:57 PM

Quote:

Originally Posted by HappyCamper1

....Just finished our inaugural trip with our 2016 Simplicity...a little curve swaying but other than that handled great!

I missed your comment on the sway. The cure is to replace the rear bump stops with Sumos... the yellow ones.

Kegan · 08-15-2021, 07:57 PM

Same problem with my Roadtrek. The only thing I have any luck with is dumping some ice in and then driving around for about 30 min and recheck. That worked. Once. Now I'm back to always reading ⅔ full. I agree with Mumkin, self monitor and dump based on usage.

HappyCamper1 · 08-16-2021, 01:12 AM

wow!!..Thanks for all the responses!...

ChicagoTom · 08-22-2021, 01:40 PM

Quote:

Originally Posted by Nspekter

I’ve had good results with the wand. Takes about 10 minutes.

100% agree. I full timed for over a year and found that this is the only sure way. My 09 sensors still work great after cleaning. Then after cleaning and dumpting the 2nd or 3rd time it'll read 1/3 or 2/3. No big concern, because it will still show when full after 2/3. I clean it about every 3rd or 4th dump. Flex wand and the chock to keep flap open while cleaning. https://www.amazon.com/Prime-Product...635776&sr=8-36

booster · 08-22-2021, 02:12 PM

The big thing to take from all of these very good comments is that it really doesn't matter how you figure out what works to clean the sensors, it is only temporary and you need to be willing to do it very regularly.

It is what we saw also and I am not one to be willing to do that much effort and messiness if I don't have to. Since we changed to external sensors I have never had to clean the tanks unless I want to freshen them up. That only entails dumping our last time before heading home putting in half a tank of water and a bit of Tide HE liquid laundry soap to slosh around on the way home

Ken Allan · 08-22-2021, 03:39 PM

There is an alternative (low-tech, non-electronic) solution... the Horst Miracle Gauge. This is based on basic hydrostatic principles that are sometimes used in industrial applications.

https://horstmiraclegauge.com/

I did a DIY version of this before I saw the Horst product. Starting with an empty tank, add 2 gallons & record the "inches of water". Add two more gallons & record. Continue till tank is full. Depending on how off-level the van is I can tell within 1/2 gallon of tank capacity.

terance13 · 08-29-2021, 11:53 PM

I just can't bring myself to drill a hole in an otherwise non-leaking tank...scares the bejeezus out of me! If I could just figure out the average amount of water used per flush I would have some idea of the number of flushes my black tank held. The grey tank is another matter....

You may also like: