sensors in black tank not working

[UK Cards Fan]

Our sensors in the black tank will not go below 1/3 full, even after emptying. It will then go quickly to 3/4, even tho it isn't. My husband times how long it takes to empty and it isn't long. So we KNOW it isn't 3/4. We have filled it with water and put a solution purchased at RV store in there. We have used Dawn, didn't work. We have had it almost empty and put ice in it, twice! We are really baffled. We don't think sensors are bad. This happened once before and we were able to "fix". Also, the gray tank sensors work fine. And no, we don't leave value open when we are parked. Any other suggestions? We will be going out middle of October again. What are opinions regarding "Happy Camper" sensor cleaner? Thanks.
We have a 2500 TS Sunseeker

[A32Deuce]

After a few uses, they are useless. When you flush and,it burps, that's when to empty. Or you can jump through hoops trying everything that is suggested on here, but it will happen again.

[UK Cards Fan]

Thanks. I will try a "wand". And use a flashlight. If we get it clean again, before it's used, there will be water in there to see if it helps!

[bikendan]

OEM holding tank level indicators have been notoriously inaccurate for decades.
Most of us just ignore them.

[Hclarkx]

Originally Posted by UK Cards Fan

Our sensors in the black tank will not go below 1/3 full, even after emptying. It will then go quickly to 3/4, even tho it isn't. My husband times how long it takes to empty and it isn't long. So we KNOW it isn't 3/4. We have filled it with water and put a solution purchased at RV store in there. We have used Dawn, didn't work. We have had it almost empty and put ice in it, twice! We are really baffled. We don't think sensors are bad. This happened once before and we were able to "fix". Also, the gray tank sensors work fine. And no, we don't leave value open when we are parked. Any other suggestions? We will be going out middle of October again. What are opinions regarding "Happy Camper" sensor cleaner? Thanks.
We have a 2500 TS Sunseeker

Most of us have had exactly the same problem. Me for five years. The lower sensor gets clogged and the ones above get a film on them and light up the instant something gets splashed onto that film and turns it opaque.

I've tried the cleaners and such and they help but not much. My built-in black tank sprayer helps if I run it long enough and often enough, but it isn't a full solution and some dump stations don't have enough pressure to make it work well.

The only solution I've found is to drill four or five holes (about 1/10 inch diameter) in a plastic hose cap so that water will spray out in all directions. I shove the hose up into the black tank through the outlet and work it so that it flops around a bit under maximum pressure. This is the only way I've gotten the 1/3 light to turn off. I probably use 40 or 50 gallons of water during this process. And within a month or two it's back.

I've read that filling the tank and adding a cleaning agent (half water softener and half spic and span is often recommended) and this helped some. Though I suspect that if I did this, then did the five minutes of a hose flopping around inside, I might have a better result. Or doing this then using the built-in sprayer (which I don't think hits the sensors very well in my black tank).

Yes, working that hose with the "water" coming out around the hose is not pleasant. Dumping well and using the built-in sprayer well at your last dump helps some but you'll still need a shower immediatly. I catch the water in a 10 gallon bucket and dump it on my oak trees where organisms in the soil quickly eat it up killing the smell.

There are after-market sensors that get fairly good reviews. There are also complete aftermarket systems that show level (in 1% steps) with just sensing strips on the outside of the tank. Pretty expensive but I think do work.

I use this religiously and it helps but again, not much. It does 100% kill odors though!!

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

You'll also probably find that the "full" light is somewhat below the top of the waste tank. I.e., you might be good for another 5 gallons or more.

But, as others have noted, it won't take long and you'll have a good sense of how full the tanks are without any sensors. Our black tank is the last one to fill, takes 12 days or more for two of us even if we dump some galley water into it to get rid of excess galley water or keep plenty of dilution in the black tank. Galley tank can fill in a few days if we aren't very careful when washing dishes. With care we can get 8 days or more out of the galley tank. After that we capture all galley waste water and move it to one of the other tanks via gallon milk jugs with a big hole cut in the top. We have our showers down to about 3-4 gallons each so that 46 gallon tank also rarely fills. We transfer galley water into it if we sense that the black tank is getting full.

Welcome to rv'ing.

[Mr. Dan]

I have a situation unlike most other users. My black tank sensors work right. My bathroom gray tank sensors work right. My kitchen sink/galley tank sensors are always wrong UNLESS I'm at home with that tank completely empty and I leave the dump valve open long enough for the tank to dry out. I've removed my sensors and found Hershey's chocolate looking stuff on the sensors although shining them doesn't help!

[hhl]

My sensors gave also false readings. Looked under rv to see where on the tank the sensors are located. In my instance on driver side of the black water tank. Black tank empty. Bought spray wand and connected to water hose. Held toilet valve open with my foot. Lowered wand past toilet pipe and sprayed tank wall from left to right while lowering wand to the bottom off the tank.
15 seconds of spraying and all the sensors are working again.

[dward51]

A habit I started with our old trailer back in 2002 or so was to do this "after" dumping and flushing as much out of the black tank as I could via normal methods (normal flush and back flush with sewer solution and the tornado flush on the tank).

I would put in 5 gallons of water, add a bag or 2 of ice (the hard cube type - two bags in hotter weather) and about 1/3 of a bottle of dawn liquid dish soap. All added via the toilet which was held open manually to give straight access to the black tank. Close the toilet, and then drive home. No dragging water hoses into the camper.

There is a state park campground near our house and the last stop was to flush and rinse the black tank again. I would sometimes do the final flush the next day if we were tired or got in late. The combined sloshing of the water, bouncing of the ice cubes with the dawn soap did a good job of breaking up any residual film, scum, or whatever in that tank. Also kept residual odors down in storage between trips as the inside of the tank was apparently about as clean as it could be.

You can do the same with the grey tank, but ice is not really an option. At least I never figured a way to get it into the grey tank.

Not expensive, and might be worth a try before you pull the sensors and replace them or start dragging a hose and one of those 90* wands inside the RV/trailer.

[TitanMike]

The problem described by the OP is common.

Problem is Toilet Paper. Unless the TP is dissolved in the tank liquids pieces float around and when tank is drained some will stick to a sensor or two.

This TP dries out when tank is empty and the indicator will show empty as a rule. Then after the toilet is used a couple times enough liquid enters the tank to wet the low end of the TP that's sticking to one of the sensors. Moisture wicks up in the TP making the sensor think there's liquid on it and "Bob's your Uncle", your tank indicator lights make you think someone just took a 15 gallon "dump".

Some ways to make this less of a problem:

Use toilet paper that dissolves as quickly as possible in water. Doesn't have to be RV specific TP as some manufacturers offer the "Quick Dissolve" stuff for people who want to use it in the septic systems. I use Scott's and rarely have this problem

Use a toilet chemical that doesn't only act like an odor control but also helps dissolve "solids", including toilet paper. I personally like "Odorlos" but have used several others in dissolving packets that work well to.

Don't be stingy with water when flushing #2. If you don't have enough water in the tank draining it is like trying to get mud to flow.

If you have a built in tank flush, use it generously. If emptying in a campground, dump the tank, let as much drain as possible, then hook up the tank flush and let it run 10-15 minutes (or more). Use a wand if you want but regardless, make sure to flush the tank longer than just a minute or two. Think of it like trying to spray a couple of inches of mud off your sidewalk. It takes time.

Another way to keep the tank clean is to dump the tank when you leave a campground, fill it around half full and drive home. Hit the last rest area dump station or local public works dump station before you reach home. That sloshing water will get a lot of sludge free and into solution so it drains well. Think of this as the rinse cycle. If you have some laundry detergent put a 1/4 cup of so in the water you added to help clean it even more.

If you are dumping at public rest area dump stations that have the straight hose that you can't connect to your built in flush fitting buy and extra winterizing fitting that hooks to your City Water fitting. Connect it to your flush connection and push the straight hose over the air fitting. It should hold while you push the button for your 45 seconds or so of water pressure. If not just hold it while someone else pushes the button.

Note: When finished with this fitting you just used on your flush connection put it in a ziploc bag and mark it "Black Tank Flush Only". Some people who have windows in their bathrooms will often put this hose through the window and stick it down their toilets to flush it out. You DO NOT want to use this fitting to blow out your RV's fresh water system when winterizing. Just keep it for hooking up when flushing the Black Tank. (I made mine from a hose adapter and air quick disconnect fitting I picked up at Home Depot and it works fantastic at Rest Area Dump Stations).

As for black tank gauges a sheet of paper stuck to the wall of the Bathroom with a crayon handing from a string next to it would do a better job. Every time someone uses the toilet put a mark under " #1, #2, or Both". This way one could get a good gauge on how full the tank really is.

Believe it or not, someone has actually studied how much feces the average human produces each day. Averages between 14 and 17 ounces (or around 1 pint give or take).

Ditto for Urine. About 4.25 pints, assuming a normal 2 liter per day liquid intake.

[bbRN]

We keep dawn soap and calgon in the black tank along with the treatment tabs. Also flush out really well after emptying.

[W5CI]

Don't worry about the tank sensors You will know when they fill up. the sink and or shower will no longer drain. and you can see when the black tank is full, but that isn't ever a problem for us. we have a 40 gallon black tank as is the Grey tank. the Galley tank is the one I have problems with the wife filling up it is only 28 gallons.

[shulkind]

Originally Posted by UK Cards Fan

Our sensors in the black tank will not go below 1/3 full, even after emptying. It will then go quickly to 3/4, even tho it isn't. My husband times how long it takes to empty and it isn't long. So we KNOW it isn't 3/4. We have filled it with water and put a solution purchased at RV store in there. We have used Dawn, didn't work. We have had it almost empty and put ice in it, twice! We are really baffled. We don't think sensors are bad. This happened once before and we were able to "fix". Also, the gray tank sensors work fine. And no, we don't leave value open when we are parked. Any other suggestions? We will be going out middle of October again. What are opinions regarding "Happy Camper" sensor cleaner? Thanks.
We have a 2500 TS Sunseeker

My TT has a black water tank flush. My sensors said the same as yours until I started using the black water flush. Now it shows empty after the flush. Do you have a black water tank flush? If yes, use it. It works great for me.

[parrott]

If you really want to know how full your tanks are, install the seelevel tank system. Accurate every 3% and easy to install as long as you can get to the outside of the tank.

[KAS]

The black tank sensors are notorious for not working. Mine always show full, even after emptying and thoroughly flushing the tank. I open the toilet trap and shine a light down to see how full it is, that seems to be the most reliable method. And if paper & waste pile up at the bottom of the pipe and the tank looks like it is full (since I use as little water as possible to flush), I use a 4-ft snow marker stick to "stir" (yes, disgusting but it works!). Keeps me from having to dump unnecessarily.

[SailorSam20500]

As noted, tank sensors regularly get gunk on them and fail to read correctly. Issue is they are metal sensors inside the tank. From what I've read, the only accurate system of sensors is the one from SeeLevel, which are external to the tanks. However, at $270 for the basic 3 tank system, seems most folks, myself included, just live with the situation.


https://www.garnetinstruments.com/rv-shop/products/

[Grapehound]

Almost all of these factory tank gauges become completely inaccurate and useless unless you go to extraordinary lengths to "clean" them.



The easiest way I have found to address inaccurate tank gauges is not to look at them.



No muss, no fuss. Inexpensive too.

[5picker]

As mentioned, the sensors are notoriously inaccurate. We all eventually learn to dump as needed.

One thing I have found over the years... instead of hitting the button for a second or two to see the tank levels... press and hold the button for 30 second or so. Sometimes that changes a 3/4 tank reading to empty after dumping.

[UK Cards Fan]

Yes, we do. And yes, it is used! We use it in the CG and for the last dump.

[emm-dee]

I use a calendar to determine if the tanks need emptying. Five days camping=time to dump the grey tank. Eight days camping=time to dump the black tank. That method has served me well for many years.

[FORKLIFMAN]

The trick with the ice, really works! Did mine last year.... Cleaned Black tank, Put in the water and ice, and drove one of the most windy roads, for an hour, worked great....

Cheers David