Cleaning Holding Tank Sensors

Well, false readings are normal and to be expected. If you don't have them, then is definitely something not right! :B

Some tanks are easy to dump and flush and some aren't because they come in many different shapes/configurations and dimensions and the outlet can be on the side, end or bottom. We've had both extremes and currently have the difficult type because it is too shallow compared to it's width & length. There is the Horst Miracle Probe that may or may not help. The Horst probes really helped on a previous TT but did almost nothing in our current TT. Another thing that can happen is that the factory sometimes installs the button sensors in incorrect elevations and they won't read right no matter what. For more a lot more $$ you can get the SeeLevel sensors that go on the outside of a tank. If you have an enclosed underbelly, changing sensors is not a simple job tho.

Preventive measures will help for the black tank - 3-5 gallons of water before use, fill tank to near full before dumping and flush/rinse as best you can before heading off. A built-in flusher works well for us (can be retro-fitted). A Valterra backflush elbow worked great on a previous TT but does nothing for our current one. If the toilet pipe drops straight down to the tank, a wand type flusher will help.

If you have a really plugged up tank or it's walls are coated with slime and short-circuiting the sensors, the best method of all for cleaning is Liquid Drano (or equiv.). Our owners manual actually says to use it. It needs to be the type that doesn't not attack metal and do NOT dump it into a private on-site septic system. We've used it 2 or 3 times and it is amazingly clean afterwards. Sadly, it doesn't take long for false readings to come back. :M

Dutch_12078 wrote:
I found the best solution for us years ago, was to replace the existing "screws through the tank wall" monitor system with an external capacitance sensor system. I like the "SeeLevel II" series that uses the existing wiring. With normal tank flushes, we've never had a misreading tank level. I also like that the SeeLevel II display reads in percentages instead of the inaccurate "Empty, 1/3, 2/3, Full" displays common on OEM and KIB systems.

I just installed the SeeLevel II as well after first trying several ways of cleaning things. So far I'm pretty happy with these new sensors and they were quite easy to install.

I don't think there really any good way. Stuff stick to them and that's whats causing the miss-readings. I have found the best way to keep them working is to dump all your tanks completely. Then add a 3-5 gallons of water and a bit of Dawn Dishwashing liquid (stronger is OK). Then take it for a good drive, or travel to your next destination.

The sloshing of water will pound against the sensors beating off anything that's stuck to them. The Dawn will help clean the tank and the sensor too.

Beyond this, there's really not much else that can be done. You can try different chemicals in your tank, but it's the sloshing while on the road that works the best.

I found the best solution for us years ago, was to replace the existing "screws through the tank wall" monitor system with an external capacitance sensor system. I like the "SeeLevel II" series that uses the existing wiring. With normal tank flushes, we've never had a misreading tank level. I also like that the SeeLevel II display reads in percentages instead of the inaccurate "Empty, 1/3, 2/3, Full" displays common on OEM and KIB systems.

Gray water tank sensors tend to get mucked up with grease - I have found that Dawn seems to be the easiest way to tackle those sensors.

Black water tank sensors tend to get much up with toilet paper and other "stuff" ... I use a "butt wand" sold at any RV outlet which you put down the toilet and use a high pressure spray to clean off the sensors. If your patient you might consider adding a bottle of septic tank cleaner to the black water tank ... fill to the brim and wait a week --- tends to dissolve everything. Many RVers tend to ignore the black water tank sensors - you kinda know when that's getting full .... gray water tank is more important in my book.

A Hearty Thank You to all that replied, I hadn't thought about using Dawn but definitely will do so. Thanks again and smooth Roads to each of you.
1Fanman (AKA Del)

Don't use city water, instead use the pump only and the fresh water level will be a good guide for dumping.

99% of the sensors are only intended for the salesman to sell the rig - "And it comes complete with a great tank monitor system."

My approach is somewhere along the line of the Geo Method (Google it). Prior to traveling, I empty the black tank and flush it out with the grey tank along with the fresh water from the internal tank rinser. When empty, I add back in about 5 gallons of fresh water, add a cap full of Calgon liquid water softener and a cap full of liquid laundry soap (I use Oxy Clean). I also do the same with the gray tank. Traveling with this solution in the tanks has (in the past) kept my sensors working properly. However, we normally sit in one rv park for most of the summer and along the end of our stay, the sensors start acting up. Once we start traveling home and using this solution, the sensors will clean up and start working again.

This also has a side benefit of eliminating any odors from the tanks.

Hope this helps

Ron

When the toilet burps, the black tank is nearly full.

When water backs up in the shower, the gray tank is full.