Black tank not fully emptying?

[chemist308]

This one has been bugging me for a while. I'm finally posting it because I'm in the middle of a black tank dump, from full to 2/3...

When I dump the black tank, if I want it completely empty I have to use the black tank flush. Otherwise it drains down to 2/3 according to my wall panel, and stays put. I can get it to 1/3 by doing several fills and flushes of the toilet. What gives? I'm using Scott RV toilet paper, and we flush with plenty of water. I noticed it used to take us a week to fill our old Jay Flight 35 gallon black, and it also takes a week to fill our Reflection 43 gallon tank from a panel read of empty--so we must be using more water. Any idea what's up here? Do the GD tanks need to be flushed every single time or could this be an issue?

[Dynamowhum]

I have the exact same issue. I bought my RV used and it came with this issue. The stealership was supposed to repair it and several other items before it left out. I didn't see it because I had to have it delivered as I don't have a big enough truck. Won't go below 2/3rds. After many phone calls to the dealership they are supposed to send out a tech. Will post what he finds.

[CloseToRetirement]

You will find that the tank monitors on RVs are horribly unreliable. You can check out this thread.

https://www.mygrandrv.com/fo...591#post193591

[CoChris]

If you are relining on the built in level indicator lights, they are know to be VERY inaccurate and highly variable. Especially for the black tank. If you are not certain of your capacity, and have the time, I have used a water flow meter (like this Amazon $15). Empty the tank as much as you can. Hook up meter to your black flush and fill tank (check level by looking down toilet. When you see water STOP. DO NOT OVERFILL). I noted the the number of gallons to turn on each indicator light. Here are my numbers when brand new (toilet had never been used). Now, after one season of use, and lots of fairly through dump & flush cycles, they are all over the place.

Indicator on panel 1/3 full, ~10 gallons
Indicator on panel 2/3 full, ~23 gallons
Indicator on panel full, ~40 gallons
Visible in soil stack, ~54 gallons

Chris

[WhittleBurner]

You may have some paper on the sensor giving you a false reading. Then when you do the black tank flush it will wash that paper off now giving you a good reading.

[lawdes]

The description defines the problem. When you do the flush, or run water again down the toilet and get better readings...that’s not because more water has drained out but rather because the “crap” covering the sensors has been washed away. If it doesn’t get washed away, or gets dried on the sides of the tank the sensors are going to think the tank is full to that level. This is an almost universal problem with the stock sensors. Consequently, unless I’m at a dump station where others might be waiting, I always run the black tank flush for at least 15 minutes and clean those sensors off..and it will read empty. You can count on those sensors being wrong, especially the black tank.

Moral of the story...take a few minutes and use that black tank flush!

Good luck!


Sent from my iPhone using Tapatalk Pro

[TwoElkhounds]

The description defines the problem. When you do the flush, or run water again down the toilet and get better readings...that’s not because more water has drained out but rather because the “crap” covering the sensors has been washed away. If it doesn’t get washed away, or gets dried on the sides of the tank the sensors are going to think the tank is full to that level. This is an almost universal problem with the stock sensors. Consequently, unless I’m at a dump station where others might be waiting, I always run the black tank flush for at least 15 minutes and clean those sensors off..and it will read empty. You can count on those sensors being wrong, especially the black tank.

Moral of the story...take a few minutes and use that black tank flush!

Good luck!

Same here, never even look at the tank level sensors as they are inaccurate. I have a clear plastic dump tank adapter that I use on the dump connection and unless there is somebody waiting behind me at the dump station, I run water through the tank, closing the dump valve to build up some volume, then release. Repeat process until the water runs clear. You then know you tank is empty and all solids are removed.

DAN

[boyscout]

This one has been bugging me for a while. I'm finally posting it because I'm in the middle of a black tank dump, from full to 2/3... When I dump the black tank, if I want it completely empty I have to use the black tank flush. Otherwise it drains down to 2/3 according to my wall panel, and stays put. I can get it to 1/3 by doing several fills and flushes of the toilet. What gives? I'm using Scott RV toilet paper, and we flush with plenty of water. I noticed it used to take us a week to fill our old Jay Flight 35 gallon black, and it also takes a week to fill our Reflection 43 gallon tank from a panel read of empty--so we must be using more water. Any idea what's up here? Do the GD tanks need to be flushed every single time or could this be an issue?

Your tank is indicating 2/3 full either because - as others have said above - the tank sensors are mucked up, or there is a buildup of stuff in the tank that has dammed up around the outlet and is preventing the tank from fully emptying, or both.

Consider using the GEO method. Put cups of Dawn dish soap and water softener down your toilet. Then fill your black tank - stick a hose in the toilet and run it until you're pretty sure the tank is full... it'll take a while. Filling the toilet bowl with the hose and flushing it repeatedly is best to keep the water roiling around in the tank.

Once full let it sit for at least an hour or two, the longer the better. If you can go for a drive with it, better still (in that case don't fill it all the way to full, leave room for water to slosh around). Then dump, turning on the black rinse AFTER you've begun the dump.

Then do it again if necessary.

No guarantees, but this should help clean the sensors and help break up any dams in the tank. It has worked for me and many others.

https://wheelingit.us/2012/03/21/rv-...he-geo-method/

[lawdes]

Your tank is indicating 2/3 full either because - as others have said above - the tank sensors are mucked up, or there is a buildup of stuff in the tank that has dammed up around the outlet and is preventing the tank from fully emptying, or both.

Consider using the GEO method. Put cups of Dawn dish soap and water softener down your toilet. Then fill your black tank - stick a hose in the toilet and run it until you're pretty sure the tank is full... it'll take a while. Filling the toilet bowl with the hose and flushing it repeatedly is best to keep the water roiling around in the tank.

Once full let it sit for at least an hour or two, the longer the better. If you can go for a drive with it, better still (in that case don't fill it all the way to full, leave room for water to slosh around). Then dump, turning on the black rinse AFTER you've begun the dump.

Then do it again if necessary.

No guarantees, but this should help clean the sensors and help break up any dams in the tank. It has worked for me and many others.

https://wheelingit.us/2012/03/21/rv-...he-geo-method/

X2! We seldom spend more than 3 or 4 nites at any location. If the black tank is not full we don’t dump before we move. Sloshing down the road is very helpful indeed. Dawn is also a great technique, but boy do you get suds at the end! I think if you will be at one location for an extended time I think black tank flushing with each emptying should become just part of your routine. Sanitary tanks just a necessary inconvenience...so enjoy that new coach!


Sent from my iPhone using Tapatalk Pro

[MidwestCamper]

Great tips. I also seem to camp at places where the dump station is always pitched away from the sewer where the black tank will hold about 4-5 gallons.