Black Tank Sensor 20% with only 1 Gal Water

[pianolaw]

I have a 2015 Int'l 27. Specs says it has a 39 gal black tank. When I empty it the sensor shows 0%. When I add 1 gal water (with 1 scoop of dissolved happy camper) it shows 20%. Basic math - 20% = 7.8 gal. Any reason why it's showing 20% with only 1 gallon of water? Is the sensor bad?

[BayouBiker]

No the sensor is not bad. The sensor is attached (glued really) to the outside of the tank and senses changes in inductance as the tank is filled with water. It should not quite go to the bottom of the tank to prevent a response similar to what you report. Hope it is installed correctly.

It is most likely due to deposits on the side of the tank very close to the sensor and it is due to the way the device detects liquid level. When you add a bit of water and especially with the salts in happy camper, the deposits on the side form an inductive loop causing the sensor to infer a higher level than actual.

So clean your tank out as well as you possibly can and try again. If it does the same, fill it half full and add three to four times the suggested amount of an enzyme based tank cleaner. Drive the trailer for a bit and repeat or drive the trailer an entire day. Then clean the tank and repeat the entire process till the sensor is more accurate. If you have done this 3 or four times with no difference then just live with the quirky behavior.

FYI, Happy Camper is a fantastic and simple chemical, it reacts with H2S, the gas responsible for the lovely sewer smell. It also digests paper. You can't find anything much better than that. I use Happy camper while the tank is filling and then just before I travel, I add the enzyme cleaner and 4 or 5 gal of water to let it slosh around and break up any deposits that might be accumulating.

[pianolaw]

Thanks Brian. I went camping last week and dumped the black tank at the state park but only put 1 gal water mixed with happy camper for the drive home (per the directions). Next time I'll follow your suggestion and put more in there so it sloshes around more while I'm driving. Thanks again.


Chris

[BayouBiker]

Glad to help any way I can. Also instead of happy camper for the drive home, use this or similar. https://www.amazon.com/Unique-RV-Sen.../dp/B0741NL8S5 . The enzymes and detergents do a much better job than Happy Camper at cleaning tanks. Happy camper is best for preventing odors and dissolving paper while the toilet is in use.

FYI, The product in the link is already extra strength so no need to triple the amount.

[OTRA15]

To calibrate your monitor —

When you are hooked up to a sewer connection, and therefore can dump easily, empty the black tank and close the discharge valve. Then take containers of a known size [the Coleman 5 gallon water jugs for instance] and dump water down the toilet, keeping an eye on the monitor. Using increments of 2 1/2 gallons +/- keep filling until the tank is full, all the while noting the percentage readout at each step.

Your 39 gallon black tank should accept eight 5-gallon containers, more or less.

You will now have an accurate as-built scale to use. The OEM monitors are notoriously random and inaccurate IMO.

Peter

[Nelson428]

I like Happy Camper and use it. Best product I have found to remove residue from both gray and black tanks to restore sensors;

https://tanktechsrx.com/about/

[SilverWind]

I make a point of doing a black tank flush at every dump stop. I've noticed that doing it regularly helps with the accuracy of the black sensor. Also, we never use toilet paper. It's known to coat tank walls.

[Pete B55]

I had the same issue. Try the Valletta wand . About $11 and no chemicals. Worked great.

Valterra White A01-0184VP Master Blaster Tank Wand with Power Nozzle https://www.amazon.com/dp/B000BGHYDO..._MdAlEb672XTGN

[Sid Arthur]

We've found on more than one occasion that our tank monitor becomes inaccurate after we've been "docked" for a while. The cure is to turn the 12V system off at the battery switch at the door. Wait a few minutes and turn it back on. Check your levels again. It's like resetting your modem, re-starting your computer. Like all things electrical, every once in a while it gets a "hang".

[OTRA15]

Welcome to the forum, and thanks for the good idea. A hard re-boot of any system is always a good idea, as evidenced by the many "Dometic stat hard reboot" posts:

https://www.google.com/search?q=Dome...com&gws_rd=ssl

Happy trails,

Peter

[Sportcenter]

I'm assuming you have the SEELEVEL tank monitor unit. If you do, this type of monitor "sees" the level of "liquid" in the tank. Most tanks however have a triangular shape if you look at them from the side. That is to say the end where the drain AND sensor is, is much deeper than the other end. This causes the sensor to "assume" there is more "liquid" in the tank than there actually is. If you draw a triangle on a piece of paper with a FLAT top, and then draw in a liquid level, you'll see what I mean. I made a small "chart" with comparison as to the monitor level/to actual content. Hope this helps. Sportcenter

[pianolaw]

Originally Posted by Sportcenter

I'm assuming you have the SEELEVEL tank monitor unit. If you do, this type of monitor "sees" the level of "liquid" in the tank. Most tanks however have a triangular shape if you look at them from the side. That is to say the end where the drain AND sensor is, is much deeper than the other end. This causes the sensor to "assume" there is more "liquid" in the tank than there actually is. If you draw a triangle on a piece of paper with a FLAT top, and then draw in a liquid level, you'll see what I mean. I made a small "chart" with comparison as to the monitor level/to actual content. Hope this helps. Sportcenter

I don't know what kind of monitor I have but this makes sense thanks

[OTRA15]

Originally Posted by pianolaw

I don't know what kind of monitor I have but this makes sense thanks

Did you see the suggestion in Post #5 about making your own "as-built" chart of percentages for the tank? Do this once as an investment in your peace of mind, and you will never have to guess again.

Peter

[pianolaw]

Originally Posted by BayouBiker

Glad to help any way I can. Also instead of happy camper for the drive home, use this or similar. https://www.amazon.com/Unique-RV-Sen.../dp/B0741NL8S5 . The enzymes and detergents do a much better job than Happy Camper at cleaning tanks. Happy camper is best for preventing odors and dissolving paper while the toilet is in use.

FYI, The product in the link is already extra strength so no need to triple the amount.

Thanks again Brian. As a follow up what should I do with the black tank while the AS is stored at home? ( I live in S. Florida so no freeze issues). Right now I put in a few gallons of water with a scoop of happy camper. Is that enough or should I be doing something different?


Chris

[ROBERT CROSS]

Originally Posted by pianolaw

Thanks Brian. I went camping last week and dumped the black tank at the state park but only put 1 gal water mixed with happy camper for the drive home (per the directions). Next time I'll follow your suggestion and put more in there so it sloshes around more while I'm driving. Thanks again.


Chris

A routine that has helped keep ours working over the years...we do not dump the black tank without driving at least 50-100mi,(think slosh), HappyCamper, and use the flush after every dump.
POI we did do the Geo Method once years ago and still add a few ounces of Dawn after every other dump.👍

Bob
🇺🇸

[OTRA15]

Originally Posted by pianolaw

Thanks again Brian. As a follow up what should I do with the black tank while the AS is stored at home? ( I live in S. Florida so no freeze issues). Right now I put in a few gallons of water with a scoop of happy camper. Is that enough or should I be doing something different?

Chris

The most important thing in managing the black tank is to tow the trailer and mix up the contents into a slurry, as Bob just suggested. If you do not put any solid material into the tank at home, what you have done is fine. Adding human waste and TP will lead to problems eventually if the trailer remains stationary.

Using the black tank without moving the rig can lead to disastrous consequences:

http://www.airforums.com/forums/f462...-a-204667.html

Good luck,

Peter

[Bob Peahl]

Now I am confused. If the black tank sensor is on the outside, how are the internal cleaning solutions mentioned in this thread able to clean the sensor?

I understand that these clean the tank - but the sensor????

[cazual6]

Originally Posted by BayouBiker

No the sensor is not bad. The sensor is attached (glued really) to the outside of the tank and senses changes in inductance as the tank is filled with water. It should not quite go to the bottom of the tank to prevent a response similar to what you report. Hope it is installed correctly.

It is most likely due to deposits on the side of the tank very close to the sensor and it is due to the way the device detects liquid level. When you add a bit of water and especially with the salts in happy camper, the deposits on the side form an inductive loop causing the sensor to infer a higher level than actual.

So clean your tank out as well as you possibly can and try again. If it does the same, fill it half full and add three to four times the suggested amount of an enzyme based tank cleaner. Drive the trailer for a bit and repeat or drive the trailer an entire day. Then clean the tank and repeat the entire process till the sensor is more accurate. If you have done this 3 or four times with no difference then just live with the quirky behavior.

FYI, Happy Camper is a fantastic and simple chemical, it reacts with H2S, the gas responsible for the lovely sewer smell. It also digests paper. You can't find anything much better than that. I use Happy camper while the tank is filling and then just before I travel, I add the enzyme cleaner and 4 or 5 gal of water to let it slosh around and break up any deposits that might be accumulating.

I concur

[Tim A.]

Originally Posted by Sportcenter

I'm assuming you have the SEELEVEL tank monitor unit. If you do, this type of monitor "sees" the level of "liquid" in the tank. Most tanks however have a triangular shape if you look at them from the side. That is to say the end where the drain AND sensor is, is much deeper than the other end. This causes the sensor to "assume" there is more "liquid" in the tank than there actually is.

I installed the SeeLevel tank sensors in our 2002 19'. Sportcenter's description is correct. For us, it is particularly true for the greywater tank. Total tank height for black or greywater is very little and having the sensor strip attached only 1/8" to 1/4" too low can easily produce the "erroneous" low level readings.

Tim

[dzwiss]

I have a similar issue with my black tank. After dumping it reads zero, but with the addition of a couple gallons of water it reads 35%. However, we are good for well over a week before we get to 100%, so I don't worry about it. The gray tank readings are much more responsive and are usually our limiting factor. Our gray and fresh tank are spot on.