Black tank problem showing 2/3 full

[ardvark16]

I went camping this weekend and the black tank filled quickly. After 2 nights the black tank showed full. I looked in the toilet and liquid was close to the top. I have a 27 gallon smart tote and it filled up but it didn’t fill all the way. My black tank is 37 gallons and even after the pump station and using the tank flush it shows 2/3 full. How can I tell if something is clogged or if the tank is really 2/3 full? I feel a bit stuck as i am going to winterize it soon. Any suggestions? If I have a clog is there a way to fix it?

[Dave Pelletier]

Ive never had an accurate black tank gauge...I suspect a sensor problem

Dave

[Brad Wilf]

5 gallon bucket, mark a line inside say at 3/4 mark, dump into toilet. Go out side bucket under valve, dump it, should be at your 3/4 mark line. If it’s not you got blockage, if its at line you got “stuff” on your sensors.

Report back, go from there.

[tuffr2]

Black Tanks need to be flushed until sensor reads empty. That might take 15 minutes or more. I never have trouble with my black tank if I use the black tank flush long enough.

[Bob_C]

And always put some water back into the tank.....

[SomeDay]

We have found our 17 year old sensors are sometimes reading incorrectly on the 3/4 full light, even after dumping (1/4 and half are unlit). We black flush for several minutes but this doesn't tend to clear it. What has cleared ours is filling up to Full with freshwater, and I mean I look in the commode to see the level of water rising = so very full, and then we drive around for a bit to swish and then dump and it's clear for the next one or two dumps. Just saying what's worked for us.

Now what we do is prior to any dumping we will top off the black tank to full at least half hour or more before we are due to get to our dump and then when we dump it has been cleared.

Others have suggested using baking soda, water sofener, dawn, (ice cubes apparently tested and doesn't work for most), and a myriad of other things. For us it's having tank pretty full before arriving at the dump and lots of water topped up to dilute well.

I'm sure there's many other suggestions forthcoming soon.

[davis2]

Put 10 gallons of water in the tank and take it for a ride. Find plenty of curves to slosh the water around, then dump.

[IC2]

A black tank sensor and sometimes even the gray will seldom read correctly after a few uses. I even tried the Horst (now Valterra) Miracle Sensors that ended up working maybe a couple more times vs the originals. The sensors as they are inserted in a tank are about 1/4" in diameter and destined to fail with what's put in that tank. Yes, you can do a super flush and yes they may work again - for a while.


The permanent fix is something like a Garnet SeeLevel system. Not really cheap nor particularly easy to install but they work and show an actual percentage of fill, not 1/3, 2/3rds etc. I used them on our last 5er but haven't on the current since we can't travel as much: https://www.garnetinstruments.com/rv-shop/

[tuffr2]

Someday - I am going to adopt your ideas. Especially fill the black tank with fresh water and drive around.

I have used ice but later I read that does not work...but I think it does and that is what counts to me.

[grindstone01]

Originally Posted by tuffr2

Someday - I am going to adopt your ideas. Especially fill the black tank with fresh water and drive around.

I have used ice but later I read that does not work...but I think it does and that is what counts to me.

Add some dish soap to the sloshing water. We use dish washer soap packets from Dollar Tree, 2 packets for a 100 mile drive with 3-5 gallons of water. It works for us and usually on the 3rd travel day, the black water tank will drain pretty clean ( I always open the dump valve when we arrive and leave open). This is after sitting for 30-60 days with FHU and the black drain tank valve left open. This has worked for us since 2012 FT'ing.

[charliez]

I've never seen accurate tank gauges. Always add water to start, and always make sure it's full before dumping. That's really the solution to it all. If your clogging up your not using enough water and your note dumping when full. I'll use a flashlight to look down the dark hole to see when it's full when I'm filling to full before dumping.

[Brad Wilf]

Originally Posted by tuffr2

Someday - I am going to adopt your ideas. Especially fill the black tank with fresh water and drive around.

I have used ice but later I read that does not work...but I think it does and that is what counts to me.

ditto..If I have left over ice when we are packing up, I will use in black tank. Usually at least 30 miles from nearest dump station..black tank still reads like new. Not saying it's the reason, but it cant hurt. Plus lots of fresh water to flush.

[Bob_C]

Post 10.........Good luck in not getting a tank decreasing in size.......I'll bet you can't get as many gallons in that tank as it's advertised size.....

[Brad Wilf]

Originally Posted by bob caldwell

Post 10.........Good luck in not getting a tank decreasing in size.......I'll bet you can't get as many gallons in that tank as it's advertised size.....

I was wondering about that dreaded pyramid..