Black Tank showing 3/4 Full After Draining

**EddieK82** · 07-02-2020, 03:40 PM

Hello,

We just got our TT back from service and the tank is reading 3/4 full, and I know I drained it before we took it to them. I just drained the tank completely and it's still showing 3/4 full. Any tips to remedy this?

**BB&LAB** · 07-02-2020, 03:55 PM

A couple thoughts come to mind. First although you drained it before service, did you verify after draining that the display read empty? Because although you drained it, unless you did a thorough flush, in other words 2-4 cycles of filling and draining after the initial dump, it is possible solids may still be in the tank and specifically on the sensors. Another thought is did you upon noticing the tank was 3/4 full try draining again, as while it may not be likely, it is possible the service facility for whatever reason used/filled the tank. Finally if you are certain the tank is indeed empty and clean, try tapping on the display in your unit a couple times and also hold the button down a few seconds as it may be a bad display.

**Kevin2282** · 07-02-2020, 03:58 PM

Typically, it's a "chunk" left on the side of the tank. I would fill the tank full with water and let it set for a day or so then use the Black Tank flush to get it clean. Let the flush run for a while. I have had the same issues with my sensors.

Kevin

**bertschb** · 07-02-2020, 04:06 PM

Virtually all standard black tank monitors are inaccurate. Tissue and solids stick to the sensors. You can delay this from happening for a while if you thoroughly flush the tank after each dump by adding 10-20 gallons of water, draining it, rinsing then filling, draining and rinsing several more times. It uses a lot of water! If the tank gets emptied without a thorough rinse even one time, the sensors are likely to start showing inaccurate readings. Most people ignore the gauge and learn when to empty the tanks based on usage.

You can buy after market sensors that stick to the outside of the tanks and those are supposed to be accurate.

**geotex1** · 07-02-2020, 04:15 PM

If you have the capability, filling the tank with warm water will help clean the sensors more rapidly given it breaks down tissue and waste faster than cold. Higher sensors on the tank wall fall victim to TP clingers.

**huntindog** · 07-02-2020, 05:04 PM

Originally Posted by Kevin2282

Typically, it's a "chunk" left on the side of the tank. I would fill the tank full with water and let it set for a day or so then use the Black Tank flush to get it clean. Let the flush run for a while. I have had the same issues with my sensors.

Kevin

I read this a lot. My experience has been just the opposite. Since I got my first TT with sensors back in 2000, I have rarely had any trouble with them.
I attribute my suscess to my RV usage not being typical.

First off I always use a bacteria treatment that will disolve waste. and of course use TP that disolves in the "shake" test
Second, we most always boondock for extended periods.
Third, We usualy have some rough roads to our campsite, which will shake up the tanks contents nicely. And it is always at least 180 miles to where we dump, at home.

The one time I had a major issue was when the TT was used in my driveway for 6 weeks (long story) when that was over the monitors were all screwed up.
I refilled the tanks, and put a triple dose of bacteria in the tanks. Let it sit for a month. Then dumped them. The sight tube was crystal clear. It looked like drinking water!
The monitors worked again.

Contrast that to typical RV use: A short trip to a campground, for a couple of days and a visit to the dump station when leaving.
Any tank treatment will not have time to work.

**boyscout** · 07-02-2020, 05:05 PM

Originally Posted by EddieK82

We just got our TT back from service and the tank is reading 3/4 full, and I know I drained it before we took it to them. I just drained the tank completely and it's still showing 3/4 full. Any tips to remedy this?

All good advice above.

To help keep sensors clean many trailer owners use a form of the "GEO Method" - google that. Dawn dish soap, a water softener such as Calgon or Borax, and lots of water can help loosen stuff stuck to the sensors, and keep stuff from sticking to the tank. Sometimes it can help to go for a drive and get a "washing machine" action going in the tank for a while.

Good luck.

**powerscol** · 07-02-2020, 05:42 PM

Fill the tank 3/4 but add 1 cup Dawn dish soap. Take the RV for a spin cycle, or do the rumba rocking the trailer for a few minutes, then drain (you want to hear the water sloshing in the tank). The Dawn will help clean things. I do a pre-charge of the 1 cup dawn and at least 5 gallons of water before use. I also try and limit the #2 usage too. The Dawn helps reduce the typical pile formation. Also reduces the oder.
Hope this helps.

**jmbopp** · 07-03-2020, 07:17 AM

I have the luxury of being able to dump at home. In addition to the on-board tank rinser I use a toilet wand and keep using it until the sensor reads "E".