Black tank always looks half full

[k9jackie]

Back from camping in my 2014.5 interstate this weekend and I'm not sure what's going on with my black tank... even when I empty it and it sounds empty after dumping, the tank light says half full. They grey tank, water and LP lights work fine. Should I take it in for service or is there something I can do first?


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Airstream Interstate Facebook group
https://m.facebook.com/groups/1399633380341777

[AWCHIEF]

The tank monitor system that Airstream uses lies.

[Protagonist]

Originally Posted by k9jackie

Back from camping in my 2014.5 interstate this weekend and I'm not sure what's going on with my black tank... even when I empty it and it sounds empty after dumping, the tank light says half full. The grey tank, water and LP lights work fine. Should I take it in for service or is there something I can do first?

As long as it's more-or-less level and you pump out until the macerator pump runs dry for a few seconds, the tank is as empty as you can get it, no matter what the indicator lights say.

In addition, the gauges are never absolutely accurate; they're only an indicator. If it shows empty it's actually just somewhere less than 1/3 full. If it shows 1/3 full it's just somewhere less than 2/3 full, and if it shows 2/3 full it's just somewhere less than completely full. The only indicator light that is completely accurate is the "Full" light. When it shows full, the tank is full.

Note that you'll never get a flat-bottomed tank completely empty even when you dump it; the only tank that could be completely emptied through a dump valve and macerator pump would have a bottom shaped like a funnel.

[Silver Burrito]

I have heard of others dumping a 10# bag of ice cubes into the toilet (with valve open of course so the ice goes into the black water tank) and then driving down the road to break any of the slug that builds up in there. When you arrive at camp you would that empty out the melted water and any of the loose particles.

Does this actually work without damaging any sensors? I have down this only once and everything seemed to work fine afterwards.

[xrvr]

A lot of old timer. aS owners don't trust the gauges. Never did, never will. Jim

[Wingeezer]

I have little use for sensors, mine have never worked reliably, and I doubt it is worth the effort to try to do much with them. Perhaps the ones on new trailers are better, I'm not sure.

For us it is not much of an issue as 95% of the time we have full hookups.

When we do not have full hookups, the black tank is never an issue as we only use it for "peeing" and it would last for weeks. In any event, a look down the slide valve in the bowl would tell you how it's doing!

As for the gray tank - you'll know it is full when the shower starts backing up!

The gray tank fills up quickly when we have no sewer connection - we'd be lucky to get more than three days out of it with normal use - even taking showers. We have a few "tricks" to make it last longer when needed!

Brian.

[k9jackie]

I rarely have full hookups at dog shows so keeping the black tank in ship shape is a MUST. Glad to know the sensor is just quirky.


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Airstream Interstate Facebook group
https://m.facebook.com/groups/1399633380341777

[Bowmans]

Not rise if this is the case with the newer sensors but a small piece of toilet paper can hang on a sensor and false indicate. Ours was doing that when we first got it and we filled the tank up and drained a few time and it dislodged. I also like the ice cube trick but have never tried it.

[Protagonist]

Originally Posted by Bowmans

I also like the ice cube trick but have never tried it.

So do I. But it's not recommended for an Interstate with macerator pump, unless you know all of the ice will melt before you get to the dump station. The macerator pump isn't an ice crusher.

[73shark]

The AI sensors are stuck on the outside of the tank. There's been reports on this forum that one or more have come unstuck. Perhaps your sensor(s) are not positioned correctly.

[Kevin245]

Most RV tank sensors are terribly unreliable. We use the foolproof flashlight method to determine fill volume.

[Sneakinup]

"Black tank always looks half full"

Does that make you an optimist or pessimist? (sorry... couldn't resist)

[jgerardi]

Sneakinup just made my day!

[73shark]

And to us engineers it means the "tank" was designed too large.

[Artvez]

I don't think the newer sensors are any better. We just bought a 19' (2015) and the black tank stays at 0 for a long time, then the next level it shows is 47, then 75.

[Artvez]

There is a guy on Youtube who tested the ice cube theory in a clear black tank he made and it didn't do anything to clean the tank. I think he goes by Fit RV if you want to look it up.

[HowieE]

The best sensor for the black tank is eyeball it through the toilet.

it is hard to envision that you could ever fill the black tank in a week from those you can haul in your van.

When we are camping without sewer we often use the black tank by pouring dish water in the toilet to keep the gray from filling. Have gone 10 days this way

[73shark]

Originally Posted by HowieE

it is hard to envision that you could ever fill the black tank in a week from those you can haul in your van.

Three adults and five grandkids can in a four day trip.

[bellastream]

Originally Posted by Sneakinup

"Black tank always looks half full"

Does that make you an optimist or pessimist? (sorry... couldn't resist)

I'm a black tank half empty kinda guy my self

[hhendrix]

What brand of tank monitor do you have. The Micro Pulse sensors are notorious for false readings. I think one of the reasons for the Micro Pulse is they probably have never been properly calibrated even at Jackson Center. There was a recent article in Airstream Magazine which goes through the entire procedure to properly calibrate all three tanks. It is quite involved but makes perfect sense. You need to drain and fill each tank and use a connection on the back of the panel during the drain and fill process to "educate" the sensors. The amount of time and water required makes me sure it was never done at the time of installation. I'm building a new shop building with a full hook up pad next to it. When that's done, I'll do the entire procedure and post the results here.