On the road and question black tank sensor

[nmiller314]

We are halfway through a three week trip and an issue has arisen with the black tank not draining or the sensor being wrong. Two days ago, I emptied the black tank and the sensor showed 45% and afterwards showed 5%. This morning, just before pulling out for our next destination, I emptied the black. It showed 15%. I completed emptying both black and gray and when I checked the level on the black, it was now reporting 90%. I poured a gallon of water in to see what would happen and it now registers 95%. Any recommendations would be appreciated. Will check back in a few hours when we get to our next destination when we will be dry docking. Hoping it’s just the sensor!

[azflycaster]

Tank sensors are subject to inacurate readings mostly due to objects on the walls of the tank near the sensors. The most acurate tool for determining the status of the black tank is a flashlight...

[SuperTrouper]

I agree with Richard. My black tank readings are all over the place like my OEM Transmission Temp gauge in my Excursion (I put in an aftermarket to measure temp.) After many attempts to calibrate, my black tank monitor will show green and empty one day and red blinking full the next. We use the fresh water and grey water gauges to estimate how much has gone to the black and keep an eye on the level "down the hole". Has worked fine for many years. Some day I may change up to a see level 2 system but so far haven't felt the need.

[uncle_bob]

Hi

How long did you run the black tank "flush" each time you emptied the tank?

Without a good flush (at least fairly often ....) the black tank can fill up with "stuff". If that's not removed, the tank capacity is impacted and the sensor stuff may well be off.

What sort of tilt was there to the trailer when you dumped?

It doesn't take much of a "tip the wrong way" to leave a *lot* in either the black or gray tanks. No, that's not 5% to 95%.

Our tanks read zero long before they are done. When they get to 5%, I'd guess they are at least a third full. Just like the empty process, the numbers are *highly* dependent both on the left to right and front to back leveling of the trailer.

Best guess: Time to run the rinse out hose for about 30 minutes. Close the outlet valve, fill it up, open it and let it empty. Repeat again and again. Great way to spend a half hour....not ....

Bob

[nmiller314]

Thanks Brad and Bob. This is my third year with a travel trailer and what you both described is very helpful. I mostly look to the grey water level and dump the black at that time.

I usually let the black drain for many minutes while I go do something else. Then a dump the grey.

I read a couple of other posts of people using Calgon and laundry detergent to keep everything in the black tank loose. I plan to do that and when I get to our next campground with sewer connection, I will use the in-tank sprayer.

Thank you again for your advice.

[Daquenzer]

I also put about 5 gallons of water in after I dump to let it slosh around a bit. And I always use the flush when I dump. I let it flush until it runs pretty much clear. I know it takes more time. But good preventative. I can't think of the last time I had a problem. I actually have more problem with the grey water tank not being accurate. Go figure.

[BGClassic]

I use the Kleen Tank formula, google it. Pinesol and Calgon bath beads. Smells good, too.

[3OnOurWay]

Originally Posted by Daquenzer

I also put about 5 gallons of water in after I dump to let it slosh around a bit. And I always use the flush when I dump. I let it flush until it runs pretty much clear. I know it takes more time. But good preventative. I can't think of the last time I had a problem. I actually have more problem with the grey water tank not being accurate. Go figure.

Every time I have not used the flush when I dump it ends up, causing me a problem for two more trips to dump station. I’ll also try to practice dumping at the location and then loading up 5 gallons of water in both tanks to drive home with some water sloshing around in there. Huge help

[Wayne&Sam]

My black tank sensor is fine. The grey tank is whacky. In the morning it may accurately read 25% but at the end of the day (warmer) with nothing added to the tank it will read 75% or more. The next morning it's back to 25%.

[uncle_bob]

Hi

Running the flush on the back tank "until pretty clear" is sort of the minimum. Unfortunately "stuff" does not all get taken care of that way. For whatever reason, a much more extensive "spray down" is needed from time to time.

Bob

[Hermes]

I don't flush the black tank unless I have driven many miles. For example on the last day of a camp trip, I don't flush at the campsite but do so at a dump site at a gas station a half mile from home. The sloshing during the trip plus the rinser when dumping cleans out the tank. In addition, I add 6-13% fresh water in the tank for the next trip, which will also slosh around.

In fact I think my black tank is cleaner than the grey, which also needs care or else the inside surface can gum up, affecting the SeeLevel reading.

[TedSz]

Originally Posted by Wayne&Sam

My black tank sensor is fine. The grey tank is whacky. In the morning it may accurately read 25% but at the end of the day (warmer) with nothing added to the tank it will read 75% or more. The next morning it's back to 25%.

My black tank level is pretty reliable. But, my gray tank level varies as others have described. It also reads 100% well before it's full.

I'm unimpressed with Sealevel.

[pboomerx]

Originally Posted by nmiller314

We are halfway through a three week trip and an issue has arisen with the black tank not draining or the sensor being wrong. Two days ago, I emptied the black tank and the sensor showed 45% and afterwards showed 5%. This morning, just before pulling out for our next destination, I emptied the black. It showed 15%. I completed emptying both black and gray and when I checked the level on the black, it was now reporting 90%. I poured a gallon of water in to see what would happen and it now registers 95%. Any recommendations would be appreciated. Will check back in a few hours when we get to our next destination when we will be dry docking. Hoping it’s just the sensor!

Happened to me several times, something is sticking to the sensor area
Locate the black tank flush input, under the city water connection
Connect hose to flush, not the hose you use for city water
Close the black tank dump valve, turn on water
Let it run until 60-80% full, open dump valve
Repeat 2-3 times
Remove hose, close valve
If problem persists after the flush then you have a bad senso, but that’s rare

Good luck

[gypsydad]

Wife just followed recommendation using the Calgon bath beads and Pinsol lemon in the gray tank as we were getting erroneous readings. (posted on another thread here recently) Anyway after a week of sitting it is now working fine again. The Happy Camper and other tank treatments we have been using over the years, lack the "coating" that water softener (Calgon) does to the tank sidewalls and also your sensor. The other "treatments" can break down the "crap" and solids, but they also can cause the sludge to build and stick to the sides. (this is what Kleen Tank guys told us) Makes sense also. Here is the recipe:

[Gleverett]

After dumping and sensor still shows contents fill up the tanks to full with water and re-drain. Usually something sticking to sides making the sensor react.

[akarakos]

I read the many answers you were provided and will add only a few thoughts. Sometimes it helps ti add the year & model of your trailer. I’m on my 3rd and each one had unique issues. When you dump the black tank fill the tank before you dump. Close the BAW valve, Fill it again and dump again. You get more stuff pulled out of the BW tank that way. Get a flashlight and look into the tank via the toilet. Never tow without having water in the BW tank. That movements while driving breaks down whatever is in the bottom of the tank. NEVER fill your tank without monitoring the water level or getting distracted doing something else. Time flies and your tank might overflow. Also, all 3 of my trailers (2013, 2016 & 2023) had the sink in the bathroom piped to the black water. Save money on the build of the trailer. If yours does, you can top it off in a campsite and dump/refill/dump that way. Just monitor it as it fills. Good luck!

[Wayne&Sam]

Originally Posted by uncle_bob

Hi

Running the flush on the back tank "until pretty clear" is sort of the minimum. Unfortunately "stuff" does not all get taken care of that way. For whatever reason, a much more extensive "spray down" is needed from time to time.

Bob

I run the flush with the drain valve open. Then I close the valve and continue to flush for a minute or two. Beware, if you run it too long you can have a flood in the trailer. But doing this a couple of times sends a lot more nastiness on its way.

[dukmon]

Originally Posted by akarakos

Also, all 3 of my trailers (2013, 2016 & 2023) had the sink in the bathroom piped to the black water. Save money on the build of the trailer.

All of them Airstreams?

[jeffb831]

Originally Posted by dukmon

All of them Airstreams?

Many Airstreams are plumbed that way.

As best I can tell, the rule appears to be: if the bathroom sink and kitchen sink are the same side, it goes to the grey tank. If they are on opposite sides, then it goes to the black.

I am not sure about models with wet baths or rear baths.

[uncle_bob]

Originally Posted by Wayne&Sam

I run the flush with the drain valve open. Then I close the valve and continue to flush for a minute or two. Beware, if you run it too long you can have a flood in the trailer. But doing this a couple of times sends a lot more nastiness on its way.

Hi

It's a two person process. One running the flush valve and the other monitoring the level. If you trust the sensor (and that's an if ....) the second person just watches that. If you don't trust the sensor, the monitoring gets a bit more fun ( use a flashlight and look down the toilet).

If you go with the flashlight approach, you may find it "useful" to turn off the flush when you do the level check. A lot depends on just how things are set up in your RV.

Bob