False Readings on Black/Grey Water Tank

[GeorgeRa]

Originally Posted by booster

There are some misconceptions on the accuracy or how "precise" the Seelevel gauges are, I think. The gauges only measure the level of the liquid in the tank, and they have a tolerance on that reading like any instrument would, but that is not the big error you will get in your daily life.


Since they only measure the level in the tank, they are only accurate for a constant crossection tank, eg one that is linear in depth vs volume as it fills. If the tank is odd shaped like nearly every class b tank is, you are only as accurate as the amount of change in crossection of the tank. This can be a very large error.


If the sensor isn't in the middle of the tank when level, it will not read correctly if the tank slopes, and if the van is not sitting level, the reading will vary depending on if the sensor is on the high or low end of the tank.


All of these errors make the reading another "approximation" of how much is in the tanks, but a much better approximation than a 2/3 light that stays on all the time


I tend to like accuracy, so I just made a crossreference chart that I have on the wall by the panel. All I did was completely empty the tanks and then fill them one gallon at a time, taking a reading from the Seelevel at each gallon in each tank. When done, all we do is look at the reading on the gauge in %, find the closest % reading on the chart and it shows us how much is in the tank in gallons left to go or gallons in the tank. Being within a gallon or two is about as close as you will come, unless you make the chart by the quart or some other smaller increment.

So, the Seelevel gauges aren't all that accurate or precise, but they are very repeatable from what we have seen, as long as you have the van at the same level between comparisons, which can be an issue sometimes. Our chart is based on level per out setup level.

I don’t have direct experience with Seelevel gauges but assume they are capacitance-based sensors and think that any solid residue on the inner surface of the tank at the sensor will cause an error. I agree that calibration can eliminate geometrical errors but residue induced error will require tank cleaning for accuracy.

There are many ways to measure the tank level. https://www.sensorsmag.com/component...-how-they-work

I believe that pressure based sensor on the bottom of the tank will be practically immune to solids unless there is now water. The simplest way to measure would be to measure bottom of the tank deflection if the tank is not fully supported on the bottom. A Velostat-piezoresistive based sensor could work. https://www.instructables.com/id/Vel...re-Sensor-Mat/

Could be fun project, but, I will stay with my Wema level gauges (float with Reed switches) for grey and fresh water tanks, no issue. A Cassette system has almost a perfect black tank level gauge, a calibrated eye.

[VTPete]

For what it's worth...
After cleaning, rewiring and re-plumbing my fresh water tank, it was working perfectly.
Then, a week later during a very humid stretch, I filled up my water tank from my house line.

Suddenly I started to get false readings about my gray tank being full even though it wasn't.

As it turns out, it was heavy condensation causing the problem! When I looked under the RV, I though I must have had a leak as the tanks were dripping water; but it was just the effect of cold water on a humid day causing enough water to create a circuit and a false reading.

After driving it down the road for 20 miles, the tank's exteriors dried off and the readings were fine.

Personally, I find it hard to "let it go" if something is broken. But, when it's just an old fashioned design flaw, I'm ok with ignoring it.

[georgelesley]

Best way to check a black tank is turn off the water, depress toilet valve pedal and look inside with a flash lite. The one thing that may help is to wait awhile after dumping. The residual liquid may fool the sensors until they dry out. Going down the road will give false readings due to splashing.

I never depend on the sensors, if you get an accurate reading it is unusual. Just learn your tanks. With our current rig I can see the fresh water tank from outside. I check the black with above peek inside system. When it is near full so is the grey usually.

[David Pouliot]

So i have Iced, Clean, Replaced sensors and it still doesn't read correctly. I spent over 1K trying to make it better and it will work for a week or two and go right back to 3/4 reading .
I would suggest if its new put it on the dealer or manufacturer to warranty it . If not it's better to live with it
After a short bit you get a feel for it being time . Best of luck

[booster]

Originally Posted by David Pouliot

So i have Iced, Clean, Replaced sensors and it still doesn't read correctly. I spent over 1K trying to make it better and it will work for a week or two and go right back to 3/4 reading .
I would suggest if its new put it on the dealer or manufacturer to warranty it . If not it's better to live with it
After a short bit you get a feel for it being time . Best of luck

If you spent $1K you could have easily had the external sensors put on for most vans, and those have been very successful in solving the monitoring problems.

[ponti33602]

Originally Posted by Roadtrek Adventuous RS1

Probably wise .... where do you keep this journal...in the bathroom?

We just experienced what appears to be a failure of the macerator..... after a long conversation with Roadtrek.... seems like we have a dumping problem.?

Probably have to get the unit replaced?

The guy on the phone said he was pretty cautious about putting anything in the tanks.. unless they dissolve by themselves........ recommended ice.....

She just keeps the sticky note on the mirror as you enter the wet bath. To us it makes it much simpler if you "self-calibrate" your flush time so you are reasonable consistent. She always then knows when we need to plan to hit a dump station.

[Roadtrek Adventuous RS1]

Originally Posted by ponti33602

She just keeps the sticky note on the mirror as you enter the wet bath. To us it makes it much simpler if you "self-calibrate" your flush time so you are reasonable consistent. She always then knows when we need to plan to hit a dump station.

Bob,

On our last trip..we discovered that the tanks won't dump...turns out that it's 99 percent certain that we need to replace the macerator...it's the last thing in line holding up the works.

While on another thread... someone said yes it happened to them around 7 years as well and our coach is exactly 7 years old......

I'm telling you this because it seems that it's a timed out sort of thing.....6 to 7 years on tires, batteries, propane sensor, and now macerator.......

Someone told me that here's the thing with an RV....

It's either broken, you just fixed it or it's about to break......

----Mark

[ponti33602]

Originally Posted by Roadtrek Adventuous RS1

Bob,

On our last trip..we discovered that the tanks won't dump...turns out that it's 99 percent certain that we need to replace the macerator...it's the last thing in line holding up the works.

While on another thread... someone said yes it happened to them around 7 years as well and our coach is exactly 7 years old......

I'm telling you this because it seems that it's a timed out sort of thing.....6 to 7 years on tires, batteries, propane sensor, and now macerator.......

Someone told me that here's the thing with an RV....

It's either broken, you just fixed it or it's about to break......

----Mark

Thx and will stay ahead of that one for sure. Please post what you replace it with....is there some super heavy duty 15 year macerator available somewhere?

I also would have simply guessed gravity may still work but guess it makes sense it wouldn't.

[Roadtrek Adventuous RS1]

Originally Posted by ponti33602

Thx and will stay ahead of that one for sure. Please post what you replace it with....is there some super heavy duty 15 year macerator available somewhere?

I also would have simply guessed gravity may still work but guess it makes sense it wouldn't.

Bob,

My rig has a permanently attached hose, really handy system that conceals in it's own channel underneath the coach...

I'm bringing the coach to the RV shop on August 28... they'll figure out what's going on.. but, I'm pretty certain it's the macerator...if NOT... they'll probably have to remove the tanks....

Yes....I will get the best macerator I can.... understand that they do fail with use.

[PhebeCarado]

Originally Posted by VTPete

For what it's worth...
After cleaning, rewiring and re-plumbing my fresh water tank, it was working perfectly.
Then, a week later during a very humid stretch, I filled up my water tank from my house line.

Suddenly I started to get false readings about my gray tank being full even though it wasn't.

As it turns out, it was heavy condensation causing the problem! When I looked under the RV, I though I must have had a leak as the tanks were dripping water; but it was just the effect of cold water on a humid day causing enough water to create a circuit and a false reading.

After driving it down the road for 20 miles, the tank's exteriors dried off and the readings were fine.

Personally, I find it hard to "let it go" if something is broken. But, when it's just an old fashioned design flaw, I'm ok with ignoring it.

Good to know. I have a 2018 Carado Benff and have the same issue. The indicator of black/grey water keeps showing it is full even right after dumping, which I am very sure the tank is empty. I don't care much about the accuracy of the indicator as I know it never been accuracy for most RVs. The problem I am facing is I can not flush water down to the toilet anymore when the indicator shows full. The red light behind the toilet bowl lights up whenever the water cannot go down. Have you experienced this situation before? Any idea how to deal with it? Really appreciate any suggestions.