Updated May 23, 2016
Both gray and black water tank levels now function reliably. The photo above was taken yesterday, after the cleaning of the gray tank. It now registers "empty" when empty, and with about four gallons in it shows 1/3 full.
After driving 250 miles with about 6 gallons of treated water in the gray tank I dumped it into a bucket. I then added four gallons of fresh water and dumped the tank. I did so one more time until the macerator discharge was clear. I pumped the tank into a bucket so I could observe what came out of the tank.
Here is what came out of the gray tank after sloshing with the water/chemical mixture:
Before adding the chemical treatment, I dumped the tank, then added about eight gallons of fresh water and dumped it again. The water that came out was clear. I then put about 6 gallons of chemically treated water into the gray tank and let it sit for a couple of days, while driving about 250 miles.
The bucket shows what was pumped out after treating.
We've stopped using a popular dishwashing liquid and have switched to Dawn. G was resistant but she now sees the consequences.
DISCLAIMER - This information is provided as my amateur observations. It is not an endorsement or a recommendation for any product or method. Do your own research and follow all manufacturer's instructions for any product or procedure you may decide to use. I bear no responsibility for results or the lack of them.
Original Post May 18, 2016
Those point level gages on RVs are frequently inaccurate. For example, the gray tank in the photo is empty but the indicator displays two-thirds full. At the same time the black tank indicator was also non-responsive.
Our tank level gages have steadily worsened and after several months in an area with hard water they no longer respond to tank level changes. We dump, rinse the tanks and fill and the indicators never change.
We've read about a variety of treatments including rinsing with a solution of Dawn dishwashing liquid, using Borax, and even dumping ice cubes into the black tank via the toilet and letting it swish around for a while. I was convinced that hard water had fouled the sensors, leaving calcium deposits. So I tried several gallons of a 6% solution of vinegar. None of the things we tried worked.
I was told over at Facebook to give up. I decided more drastic measures were necessary.
I decided to try a chemical for the purpose. I followed the manufacturer's directions except I used a weaker solution. After putting about three gallons of a water/chemical mix into the empty black tank we continued on our trek and drove all day. About 12 hours later I dumped the tank, filled it with clear water and dumped it again.
After cleaning and dumping here is what the [black] tank indicator displays for an empty tank:
To test the tank sensor I again rinsed and dumped, It showed empt. I then poured two buckets of water into the toilet. That's about 3 to 4 gallons of water. The tank level indicator then showed two LEDs, or about one-third full.
I then pumped the contents of the black tank into a bucket. After dumping two buckets the tank was empty.
I then rechecked the tank level sensor and it again showed one LED which is an empty tank. Apparently the chemical cleaning had worked.
I'll next do the grey tank, but I'll have to wait until we have an all day trek so I can again let the mixture slosh around while we drive.
What Did I Use?
Before reading on I suggest you read the following disclaimer. I am neither promoting or recommending any treatment or product. I am reporting my personal experience. Yours might be different.
USE AT YOUR OWN RISK.
DISCLAIMER
All content in this blog is provided for information purposes only. The information contained here should not be consider “expert” and not taken as specific advice. The author makes no representations as to the accuracy, completeness, or reliability of the information on this site or that is found by following any link. The information contained here and in the links may become outdated.The author will not be held liable for any errors or omissions in this information. The author will not be held liable for any losses, injuries, or damages from the use or display of this information.
The product I used is "Happy Camper Extreme Holding Tank Cleaner."
Note: Follow the manufacturer's directions.