I haven't seen that type before. Do you know what company makes them, maybe a name on the display or have a manual for them?
Sometimes a tank can get so much sludge build up on the walls that even the outside type can not work right. That's the case with my SeeLevel sensors, black tank and galley tank don't work well if I'm boondocking a lot as the tanks get a build-up versus hookups where I can use a ton of water and flush them out. But my fresh tank and shower tank always are accurate since they don't get dirty.

That may be the case because my fresh water hasn't had issues yet. But every time I empty my black tank I do a really good flush. The empty, 1/3 and full work on the blank tank it's just the 2/3 and it's never worked so I was thinking that sensor was probably bad; I wish I knew how to test them. No one wants to go from 1/3 go full on a black tank! The gray is annoying that it says 1/3 full when I've emptied it. Any recommendations on products to clean the gray tank? I'll look for the sensor vendor info.

Thanks! Lisa

I have heard from a few people over the years to try dumping a few bags of crushed ice into the tank with some water just before driving/sloshing around. Never tried it or had issue with our gauges but it could be worth a try and doesn't cost much.

I gave up on the sensors awhile ago. When the black tank is getting full, it makes a fairly distinct gurgling sound when you flush the toilet. When I hear that sound, I know it’s time to empty the tank. I’ve also found that after a few years, I kind of got a feel for how fast the tanks were filling, depending on how much we were using them.

As far as the ice trick goes, it certainly is worth a try. This guy tested it out and made a video. The results weren’t that great if I remember correctly.

The best way I have found to get the tank clean is fill it with clean water and some dawn dish soap. Let that sit for a couple of days and maybe drive around then empty it. I’ve had pretty good luck with that.

Yea, I love TheFitRV and saw that video. I'll try the dawn trick and see if that helps. Thanks!

After about a month on the road, my sensors are shot! Just after dumping, I still show 1/3 full on both grey and black. The next day they both may say 2/3 full.

They are bogus readings. I see thick chunks of stuff in my dump hoses so I know that there is an old build up of crud that is starting to break up. After a trip, I try to clean the tanks. My method is to start with a normal dump with a good flush. Next step is to dump a LOT of liquid automatic dish washer detergent into the tanks, fill them with water and let them sit for a few days (or more). Then repeat.

Last summer, I did some camping in Ohio, Michigan, etc. and the state parks apparently never heard of self draining water faucets as their sites did not have water on site. They said that it was to prevent freezing but I think they were just cheap. (commercial parks all had water) The main thing was that I had to use my fresh water tank almost exclusively. Since all of my tanks were the same size, as long I had fresh water then I wasn't filling any of the other two tanks.

I wasn't staying at any one place for a long time so it worked out that when I dumped then filled the fresh water, I was good to go.

I have read that you should wait until the black tank is at least 2/3 full before dumping. This is to prevent the poop pyramid and keep everything floating.

Anyone have any thoughts or experience with this?

We have been full-timing since 2008 and came to the realization like everyone else that the tank flush mechanism does not cover the whole tank like we would like, in fact it is largely water pressure dependent even though it still does not give the dishwasher experience we all envision.

Some luxury fifth-wheel manufacturers add flush mechanisms to their gray water tanks, that still isn't perfect. Some folks add a mixture of Calgone and Epsom Salts to let it soak overnight, we haven't tried that yet. When we are Workamping or Camp Hosting with an abundant supply of water we fill the gray and black tanks up several times in a row with the flusher running ... I put my phone timer on for two minutes each. I do not show this to our campground guests as more than a few have overflowed their tanks while getting distracted. That has kept things running better until our next dry camping session.

Fresh Water tanks in Florida grow a lot of algae while in storage, I also see it growing inside the water hoses that are exposed to sunlight , so those hoses also need to be sanitized or replaced on a regular basis when camping in warm sunny climates with full-hookups.

Try Commando tabs from the RV stores. Best cleaner I have ever found for hard deposits or sludge

Here’s a link for the stuff I use. Works great. https://www.amazon.com/gp/product/B06X9DQWNK/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

https://youtu.be/wUWGlm2gQfE
This video explains it all and TR's method works.

I can't seem to find the vendor who made these sensors but I'm trying the Calgon + detergent solution when I leave in 2 weeks. I'll report if it worked. Thanks!

Would this work even if I have external sensors?

And this works for external sensors too?

I think it cleans the buildup on the walls of the tank, so I think it would work for external sensors. Certainly worth a try..

Thanks, here are some others I've used - https://www.loveyourrv.com/favorite-rv-waste-holding-tank-treatments-love-rv/
Tank Techs RX would likely work well but needs to be left in the tank long enough for it to get going.

Thanks Ray, I'll have a look. I just wish all the Happy Camper stuff I'm using would do better.

Every time I move our rig I empty out our tanks and then I mix up a gallon or so of warm water with dawn dish detergent along with a cascade dish washer puck and place in both tanks. It has successfully cleaned and restored our level indicators each time. It would seem the agitation while driving is enough for the detergents to clean the tank walls. Rv

Wow, that's a great idea. I saw a YouTube video on using Borax and Zep cleaner, I'm trying that now. Thanks!