understanding tank level lights

[Mike G]

Not getting into the issue of accuracy (as sensors get dirty and whatnot), but I want to ask how the light panel is designed to indicate the tank levels. Marks are at E, 1/3, 2/3, and F. If the lights on the panel show a tank at 1/3, is this supposed to mean that the tank level is somewhere between 1/3 and 2/3, or between E and 1/3, or (perhaps ideally) rather close to but maybe somewhat more or less than 1/3 full?


Here's why I have started to wonder about this. If the sensors are meant to show 2/3 only when they are at least 2/3 full, then the fresh tank could be 60% full and yet show only 1/3 (which doesn't seem intuitive). But on the other hand, that would be okay for the tanks that are gradually becoming filled (rather than emptied like the fresh tank) since a 2/3 reading would indicate that capacity is very nearly reached. IMO the ideal way to have the lights set up would be to indicate 2/3 when the capacity is "closer to 2/3 than to either 1/3 or full," but maybe that is wishful thinking.

[Centex]

If your E19 is similar to my 5.0 an easy experiment you could conduct on the FW tank to likely answer your questions ....

• drain the tank via the petcock
• slowly fill while a companion watches the monitor lights
• as each illuminates look at the water level relative to the obvious sensor locations on the tank (flashlight can help spot the water level accurately)
• FIll completely then slowly drain the tank using the petcock and watch / note the same as you empty the tank

That should reveal if the water level must be 'close' to a sensor or actually touching the sensor, and ~where that is relative to the total tank depth both 'filling' and 'emptying'.

That liquid/sensor relationship should hold for the grey and black absent the effects of 'tank scuzz'.

On the 5.0 the grey tank sensors are also easy to see under the trailer; the black tank sensors can be seen by removing the jack access panel in the propane compartment on the driver's / toilet side, not sure about the location on the E19 but perhaps those are accessible, too.

Just for your consideration if inclined to empirical experiments, Have Fun!

Edit - ooops, yes, all moot if you've got spray foam!

[KirkB]

There is no magic in the tank sensors. The tank sensor light illuminates if the sensor it is attached to is submerged in liquid (fresh, grey or black) and can complete the electrical circuit. If there is residue on the tank wall, that might also conduct.

I don't know how precise ETI is in placing the sensors in each trailer they build. The 2/3 sensor might not be at a 2/3 level. But if it lights up, then the liquid in the tank is covering (or near to) the sensor. If you don't have spray foam underneath, you can see the sensors on fresh and grey tanks, the 2/3 sensor may not be at the exact level of 2/3 full.

If your trailer is parked off level, then if the sensors are on the low side, then there could be less in the tank than is indicated. I usually eyeball the fresh tank instead of relying on the sensor light if it says less than 2/3 full.

[oldwave]

There are service providers that will do a deep clean of your black tank and likely make the sensors work again. Other options are too replace with a sea level system, or perhaps a mopeka Bluetooth system. I know Johnny Hung has just installed the Mopeka. I have a sea level that works well.
I am not sure about the cost of the black tank cleaning service, but the RV training academy YouTube channel had a segment on Royal Flush RV

[Chama]

We recently filled our FW tank in order to sanitize the system, then driained it and refilled it to flush out the clorine/water mix. At least on our trailer, for FW, the 1/3rds and 2/3rds lights came on pretty quikly and then it took substantially longer to fill the final 1/3 to reach Full reading with water coming out of the overflow. The lights are prehaps depicting 1/4, 1/2 and Full as a guess rather than how they are marked. I can't comment on the lights for grey and black tanks.

[Mike G]

Interesting, thanks. I appreciate knowing how the sensors are meant to work.

I do have spray foam, so visuals are not possible. I think the sensors are acting fairly well, not giving readings that are wildly off. Lucky me... or maybe the previous owner gave them a good cleaning before selling. I was wondering why my fresh tank dropped from full to 1/3 more quickly, when I figured there should still be close to 2/3 remaining. Now I understand that.

On the other hand, the black tank seems to jump to 2/3 rather more quickly than expected, but I think that might have something to do with the tapered shape of the tank (or it could be the sensor placement). What I mean is, while stationary at a campground for 3 days the black tank lights went from 1/3 to 2/3 even though I believed it was only about 1/2 full. Perhaps one day I will use a gallon jug to measure and pour water in through the toilet and see how many gallons it takes to change the lights; I can also gauge visually (looking into the tank) what the levels look like, for future reference.

[MVA]

The tank sensors (fresh, black or gray tanks) are a set of probes in the tanks electrically connected to a resistor pack. As the tank fills up to a probe (or empties below a probe) the resistance between ground and a specific probe changes based on the set resistance in the resistor pack. There is a nice explanation on the RV Life Forest River forum:
https://www.forestriverforums.com/fo...es-131266.html

I have spent some time (unfortunately) diagnosing level indicator issues. What I have discerned is that probes are close to the correct location in the tanks but not quantitatively correct. So if the tank reads just 2/3 full as you are filling it, it could be 1/2 - 3/4 full. Also, foreign material and soap scum in the tanks can give erroneous readings. So in the case of filling a tank (referring to the diagram in the link) once the liquid reaches the 1/3 probe, the resistance pack should read 186k ohms. But if there is a conductive path between the 1/3 and 2/3 probes (e.g., soap scum in the gray tank, toilet paper in the black tank), the 2/3 probe will light since the conductive path has a lower resistance of 68k ohms.

Practical advice is to flush the black tank with a cleaning wand like:
https://www.amazon.com/Valterra-A01-.../dp/B000BGHYDO

For the gray tank, I have switched to using Dawn for cleaning dishes and that has seemed to keep the soap scum in the gray tank under control. Time will tell.

[Bea]

Originally Posted by MVA

For the gray tank, I have switched to using Dawn for cleaning dishes and that has seemed to keep the soap scum in the gray tank under control. Time will tell.

We use Dawn, too. However, last year we noticed that our 1/3 gray tank sensor light used to come on all the time - no matter what we tried. We suspected some sort of build up on the sensor so we decided to try and switch to Sulfate free shampoos and conditioners. What a difference! After a few uses and tank rinses, the 1/3 sensor light went off and now works as it should. Crazy how little things like this can make your day!

Unfortunately, however, with this change we also noticed that the tank valves were starting to get sticky. So now we add a little bit of lubricant like this https://www.campingworld.com/thetfor...B&gclsrc=aw.ds in addition to our normal treatment after we empty our tanks. So far so good!

On a side note, we use this https://www.amazon.com/Save-a-Drop-P...89&sr=8-7&th=1 along with this https://www.campingworld.com/flush-king-20522.html when we flush our black and gray tanks (when we are at a place with hook ups). We also use this https://www.amazon.com/LASCO-05-1760...s%2C145&sr=1-2 to keep the water meter free from contamination from any waste water. This set up lets us know how much rinse water is going in the tanks without having to constantly look in the toilet or use the light sensors inside. But in your case Mike, this little water meter could also be used to help determine how much you are putting in your fresh water tank to determine when your sensor lights come on. Hope this helps! -Bea

[MVA]

Originally Posted by Bea

We use Dawn, too. However, last year we noticed that our 1/3 gray tank sensor light used to come on all the time - no matter what we tried. We suspected some sort of build up on the sensor so we decided to try and switch to Sulfate free shampoos and conditioners. What a difference! After a few uses and tank rinses, the 1/3 sensor light went off and now works as it should. Crazy how little things like this can make your day!

Unfortunately, however, with this change we also noticed that the tank valves were starting to get sticky. So now we add a little bit of lubricant like this https://www.campingworld.com/thetfor...B&gclsrc=aw.ds in addition to our normal treatment after we empty our tanks. So far so good!

On a side note, we use this https://www.amazon.com/Save-a-Drop-P...89&sr=8-7&th=1 along with this https://www.campingworld.com/flush-king-20522.html when we flush our black and gray tanks (when we are at a place with hook ups). We also use this https://www.amazon.com/LASCO-05-1760...s%2C145&sr=1-2 to keep the water meter free from contamination from any waste water. This set up lets us know how much rinse water is going in the tanks without having to constantly look in the toilet or use the light sensors inside. But in your case Mike, this little water meter could also be used to help determine how much you are putting in your fresh water tank to determine when your sensor lights come on. Hope this helps! -Bea

Great ideas!

Interesting on the shampoo. When I cut the gray tank exit line and examined the inside of our gray tank, I saw what looked like "drain scum" on the tank walls. After cleaning the inside of tank around the sensors with Dow bathroom cleaner, the tank sensors have worked well.

[Mike G]

Originally Posted by Bea

Unfortunately, however, with this change we also noticed that the tank valves were starting to get sticky. So now we add a little bit of lubricant like this https://www.campingworld.com/thetfor...B&gclsrc=aw.ds in addition to our normal treatment after we empty our tanks. So far so good!

That might be just what I need for my gray tank valve. Thanks for mentioning it!

[Bea]

Originally Posted by MVA

Great ideas!

Interesting on the shampoo. When I cut the gray tank exit line and examined the inside of our gray tank, I saw what looked like "drain scum" on the tank walls. After cleaning the inside of tank around the sensors with Dow bathroom cleaner, the tank sensors have worked well.

Originally Posted by Mike G

That might be just what I need for my gray tank valve. Thanks for mentioning it!

Sure thing! But I can't take credit for this. I read about the shampoo from an article and the lubricant and rinse set-up from a very sweet couple that we met at the Osoyoos rally last year. Rallies (and this forum) are such a great way to meet the kindest people and discover your need for gadgets and things that you can no longer live without! -Bea