Question about 3810MS holding tanks

[ebds2019]

Hi. I have gotten a little confused about my holding tanks. On the internet it always says 1 grey tank and 1 blank tank. But if that were true why would there also be a galley tank valve?

And on my control panel where you check your tank levels there are two grey tank buttons and two black tank buttons. After emptying and flushing my black tank, one of the level buttons shows empty but the other one does not show empty.

So what's the deal with the tanks. How many physical tanks are there really? And why are there two black tank level buttons, one of which never shows empty?

Thanks ............. Rob

[jeffba]

You should have 2 gray and 1 black for you model. when you get bath a half you will get 2 black tanks. Panels are standardized so you have extra buttons.
For your second gray valve you should look around your wheels. bend way down and look up by your frame

[ebds2019]

I know where my flush valves are for the two grey tanks and black tank. But then why does one black tank level always show about 2/3 full if it doesn't even exist?

[jeffba]

Could be a wire touching he frame.. not sure

2/3s tanks is most likely the real reading.

black tank gauges are just for looks

[DQDick]

That's probably the one you're actually using. Crud on the sensors is a common black tank issue with all kinds of suggested ways to fix it. I tried most of them with no success and then added outside the tank sensors and that solved the problem. The thing is that once you know how often you need to dump and establish a schedule you won't ever look at the sensor again, so we didn't add them to the new rig.