Black Tank Sensor Bypass

We are about to leave on a short trip to Assateague National Seashore so we thought it would be a good idea to test the newly replaced toilet before we leave.  It was a good idea because we pressed the pedal and nothing happened.  The toilet is not working.  After the initial panic settled we remembered that the black tank sensor sends false readings to the toilet sometimes and when this occurs the smart toilet shuts all operations down to prevent the toilet from overflowing.

We checked the black tank display and it was showing as completely full even though we were pretty sure that it is almost empty.

There are several steps to take to rectify this situation:

Reality check

The obvious is to make sure that the black tank is not actually full.  When did you last empty is?  How much did you use it?  Are you sure that the sensor is not showing an accurate reading?  The last thing that you want is for your toilet to overflow…

Reset the batteries

Sometimes this is enough to convince the sensor that all is well.  If your toilet stops working try turning everything off and reset the batteries. It did work for us the last time that the toilet didn’t work, but not this time.

Loosen up

Drive around and let things to slosh around a bit and it may show a more accurate reading.  We usually put a bit of Pine Sol in the tank to prevent any build up inside the tank.

Cut the sensor’s wire

This is a simple hack that was introduced by Seong from the Sunlight and Carado Facebook Group and is a quick and easy fix.  If the display shows full tank and you know that it isn’t full, find the yellow wire that connects to the toilet and cut it to disable the sensor.

Install connectors on the wire

We decided to take it one step further and install connectors so that we can reconnect the wire once the sensor is getting a true reading again.  We like having the warning when the black tank is actually full and the toilet doesn’t flush as a precaution.  This simple installation can be done with minimal knowledge, cost, or effort, so why not?

To install the disconnects you will need:

Male/female connectors (or disconnects).

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A Philips screwdriver and a wire cutters.

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Remove the small cap that covers the Philips screw

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Unscrew the screw and pry open the cover

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Cut the yellow wire on the van side of the white plug/connector (so that you do not void the toilet’s warranty) and strip the end of the wires.

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Insert the ends of the wires into the disconnects and crimp to secure in place.

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You can now connect and disconnect the sensor as needed.

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Make sure that the clips on the toilet cover are aligned properly and put the cover back on the toilet.

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If you want to do an even fancier job, you can install a switch that will allow you to turn the sensor on and off without having to open the toilet cover.  It really depends on how often you get a false full tank reading that will prompt you to disconnect the sensor.

BY THE NUMBERS

  • connectors (a pack of 4 pairs): $3.50
  • time to install: 5-10 minutes.

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8 thoughts on “Black Tank Sensor Bypass

  1. BACK ROADS AND OTHER STORIES says:

    Thanks! Let me know if you find a good location for a switch (one that doesn’t compromise the toilet too much…). We are thinking of doing this when we get back. Tony is thinking of putting it on the back wall where the piping and electrical go through.

  2. 365vacay says:

    This is great. My black tank monitor has never been accurate. Luckily, my toilet hasn’t stopped working after it reads full. Still, I’m sure it is only a matter of time.

  3. BACK ROADS AND OTHER STORIES says:

    Thanks! Ours was full several times and was still working, so who knows…I think that full on the display is a matter of perspective. it is possible that the sensor cuts operations when it thinks that it’s “really full”, while what we see on the display is “sort of full” 🙂 Hopefully, you won’t have to worry about it!

  4. Cameron says:

    I assume you have a camper van? Mine disables when it THINKS it’s full (when it’s completely empty). It seems like from these other comments that they don’t own an RV that has this “disable feature” like our van does.

    • backroadsandotherstories says:

      Yes and yes! The sensors are set to stop the flushing if the black tank is full, but since they don’t work very well, they think that the tank is full when it isn’t and the toilet stops working. Bypassing them eliminates the issue and lets you flush. At the same time, you need to be diligent and not let your black tank become too full.

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