Black-water tank shows full after dumping

[stan4o]

1997 Triple E embassy E27 class A motor-home
Black-water tank displays full in the control panel after dumping. Is there any trick how get everything dumped?
in fact it was showing 4/3 full. It is Tank #2 (the first one on the left on the control panel photo)
I added tap water directly through the toilet (and now waiting)...
Is there something else I can do to empty the black-water tank?


Thanks,

 

[DonTom]

1997 Triple E embassy E27 class A motor-home
Black-water tank displays full in the control panel after dumping. Is there any trick how get everything dumped?
in fact it was showing 4/3 full. It is Tank #2 (the first one on the left on the control panel photo)
I added tap water directly through the toilet (and now waiting)...
Is there something else I can do to empty the black-water tank?


Thanks,

It probably really is empty. Don't believe black tank sensors. They are usually full of ****.

-Don- Reno, NV

 

[Kirk]

The cheap level sensors used in most RVs are also very sensitive to any residue that remains on the walls of the tank when you have dumped. The tank is probably actually empty. If your toilet dumps directly down into the black tank like most RVs do, you can hold the toilet flush valve open and look into the tank with a flashlight to see if it is really empty. I would bet that it is.

 

[stan4o]

The cheap level sensors used in most RVs are also very sensitive to any residue that remains on the walls of the tank when you have dumped. The tank is probably actually empty. If your toilet dumps directly down into the black tank like most RVs do, you can hold the toilet flush valve open and look into the tank with a flashlight to see if it is really empty. I would bet that it is.

Hi Kirk, so if I put a stick in the toilet I might be able to determine if it is empty or full and how much? - correct...

Another thought: I added tap water to black water tank through toilet directly and the state of sensors changed... which makes me believe it was really 3/4 full for now it shows 4/4 full.

in short it might not be a dirty sensor issue but dry stuff inside the tank (I bought it as it is. don't know how long the tank has not be dumped)...

therefore I left the water (I added 1/4 tank) and will see if something happens in a few days... I was wondering if there is some kind of chemical I can add in the tank то dissolve the content if needed...

 

[Kirk]

Hi Kirk, so if I put a stick in the toilet I might be able to determine if it is empty or full and how much? - correct...

Most likely you can as most toilets sit directly over the black tank and the flush drops straight in. You may want to use a light too as it will help to see what you are doing. While it is possible that there is still solids in the tank it wouldn't seem to me likely that it is as much as 1/2 tank since the dump line leaves the tank at the bottom. If it were half full the drain line woud typically be blocked.

The sensors are suspect as very few of them work well for much use because they use such a primitive system. It is just some buttons at different levels of the tank and one at the bottom and a voltage is applied to the bottom button and if a button see a voltage it assumes that the tank is full to that button. The residue left behind by the human waste and toilet paper conduct enough to trigger false level indications.

Before you spend a lot of time and effort trying to clean the tank you need to be sure that it isn't empty as we suspect. If you know how large the tank is you can check that by adding water with a 5 gallon bucket to measure it to see how much it will hold before it gets full.

 

[Ray-IN]

Dried toilet paper is very difficult to remove from whatever its on; I have in the past used TSP washing powder in a 3/4 full tank during a days travel. When I got to a FHU CG I drained the tank then used a spray flushing wand to clean the tank walls, which is where sensors are located.
Here at home my outside hydrants are full water company pressure, usually 100psi. It's easy to clean the inside of the black tank with that pressure.
Once I learned the tricks to avoiding black tank problems I've never had an issue again.
Use lots of flushing water, enough to keep all solids completely covered. We have a special trash can in the commode room for used toilet paper only. NO TP goes into the black tank.
Some folks think that's gross; most of Mexico uses the same method, as they use septic systems instead of municipal wastewater systems.

 

[RVRAC]

Those sensors are not worth it. I can empty all the tanks and they would not read empty.

 

[Bob K4TAX]

I don't trust any of the sensors, black tank, grey tank, or battery ones. When we empty the tanks, when the black tank stops running, I open the grey tank valve. When it stops running, we are through. As to the battery sensor, when connected to shore power the battery is charging and the sensor shows the charge voltage and not the battery voltage. When not on shore power, the sensor shows about the amount of charge. I prefer my digital readout over the ID 10 T lights.

 

[skydivemark]

As others have said, holding tank sensors are often unreliable, especially black tank. After a trip and emptying the tanks I refill them to as full as reasonably possible (I don't use any chemicals or soaps) then empty them again. I do it twice and SOMETIMES the sensors start working again. Even if they start reading correctly they generally start giving erroneous readings a day or 2 into the next trip.
Through time we've learned by the sound of the flush how full it is and when it's time to empty.

 

[stan4o]

1997 Triple E embassy E27 class A motor-home
Black-water tank displays full in the control panel after dumping. Is there any trick how get everything dumped?
in fact it was showing 4/3 full. It is Tank #2 (the first one on the left on the control panel photo)
I added tap water directly through the toilet (and now waiting)...
Is there something else I can do to empty the black-water tank?


Thanks,

Following Kirk's suggestion I measured the level in the black-water tank with a stick and it is full - see photos.

I also ordered online Black Tank cleaner – Unique RV Digest-It - RV Digest-It Holding Tank Treatment | Liquid - hope to get it sooner. Video

- Will keep you posted.

 

[JudyJB]

Unless you are not going to use your black tank for a few weeks, it is unlikely that any "digester" is going to stay in your tank long enough to do anything. If you DO want to use it, make sure you add enough water so that whatever clog might be there can dissolve. (Also, leave a few gallons of water in your black tank when you are done flushing it and while it is being stored to prevent stuff from drying into a new hard substance that will not flush.

While you are waiting for this chemical to arrive, try adding water to your tank and see if you can use that stick to do some stirring to see if you can break up whatever is in there, assuming you really do have a Pyramid of Poop or a Pyramid of TP. (I had the latter after some small children left.) Also, you want to make sure the stick is strong enough NOT to break off in the tank and cause even more of a problem.

I broke up my TP pyramid by adding water, stirring with a strong rod, and then going for a drive to slosh things around. I found a quiet, country road where i could make some sudden stops and swerves without someone thinking I was driving drunk. Then I went back and tried to dump again. This took a couple of tries over two hours, but worked.

After some experience, you can tell when your tanks are emptying properly by the whoosh noise and watching what comes out. (The latter requires one of the clear connections.)

A last ditch solution, which I used recently when my grey tank would not dump, was to find an RV service place which can flush out your tank. And then educate your family and friends to use as little toilet paper as possible. And remember to store it with some water in it, especially if you live in a dry climate.

 

[JudyJB]

One important question no one has asked--Since this is a unit your purchased as is, have you ever been able to completely dump this tank?

The worst scenario is that someone put something down it that will never flush--like an article of clothing, a chunk of plastic or another substance, etc.

 

[John From Detroit]

I have used digesters when I was trying to extend tank life... Not sure they helped...Logically they won't but in 15 years of full timing the only time the sensors showed empty was when I did a very heavy duty cleaning with a home made version of the Valterra Master blaster.

NOTE> the Valterra product does not look well built.. Mine was better.

 

[Rene T]

One important question no one has asked--Since this is a unit your purchased as is, have you ever been able to completely dump this tank?

The worst scenario is that someone put something down it that will never flush--like an article of clothing, a chunk of plastic or another substance, etc.

My Brother-in~Law had a similar problem. Someone broke into their trailer and threw a empty soda can down the toilet. They. chased the plugged toilet/tank issue for weeks. Finally they had to disassemble the drain piping and drain valve and there it was.

 

[Kirk]

I measured the level in the black-water tank with a stick and it is full - see photos.

Not a happy answer but at least now we know. I have read the website of Unique RV and find them to have a lot of very good information so have wondered how their products are. I have been unable to locate anything to tell me the type of product it is but I think it is a biological product, probably either enzyme or bacterial, possibly a combination of both. Those are what I would use but it is important to remember that products to clean waste tank sensors are not designed to deal with a thick buildup like you seem to have but only to remove a residue from the walls of the tank. For that reason it may not work, or it may also take a very long time. I would suggest that you need to give it at least a week and a month might be even better and it would also probably make it more likely to work if you use some means of agitation of the RV waste tank. I read the reviews and they deal with a residue effecting the sensors and not a tank that is 3/4 full of dried up solids.

I am looking at your pictures and it looks like you have about 12" of depth inside of the tank. Did you measure the depth of the tank on the outside to compare that to? It takes 7 1/2 gallons of waste to fill 1 cubic foot of space so if your tank is 1 foot tall and 2 feet one way and 5 feet the other it would hold 50 gallons.

Keep us posted on how things go. In the mean time I'll continue to look for someone who has had the problem that you have and how it was resolved.

50 Gallon RV Holding Tank 53" x 27" x 10 1/2" Elkhart Plastics​

 

[Ray-IN]

Stan4o that's not your best cane pole you fish with is it?

 

[stan4o]

Stan4o that's not your best cane pole you fish with is it?

Correct...

 

[stan4o]

Not a happy answer but at least now we know. I have read the website of Unique RV and find them to have a lot of very good information so have wondered how their products are. I have been unable to locate anything to tell me the type of product it is but I think it is a biological product, probably either enzyme or bacterial, possibly a combination of both. Those are what I would use but it is important to remember that products to clean waste tank sensors are not designed to deal with a thick buildup like you seem to have but only to remove a residue from the walls of the tank. For that reason it may not work, or it may also take a very long time. I would suggest that you need to give it at least a week and a month might be even better and it would also probably make it more likely to work if you use some means of agitation of the RV waste tank. I read the reviews and they deal with a residue effecting the sensors and not a tank that is 3/4 full of dried up solids.

I am looking at your pictures and it looks like you have about 12" of depth inside of the tank. Did you measure the depth of the tank on the outside to compare that to? It takes 7 1/2 gallons of waste to fill 1 cubic foot of space so if your tank is 1 foot tall and 2 feet one way and 5 feet the other it would hold 50 gallons.

Keep us posted on how things go. In the mean time I'll continue to look for someone who has had the problem that you have and how it was resolved.

50 Gallon RV Holding Tank 53" x 27" x 10 1/2" Elkhart Plastics​

No, I have not measure the tank outside yet.
I will add the Digest-It tomorrow and see what happens by this weekend...

 

[JudyJB]

Just looked at the video. What I would have liked to see with the dog food test was two containers--one using the "disgester" and one with just plain water in it. That would have told me whether it was the "disgester" that worked or the water added to the chemical.

 

[Kirk]

No, I have not measure the tank outside yet.

If I read your measuring stick right it was more than 1 foot to the bottom of your tank and if so, it is probably empty. If that distance was up and into the toilet bown, then it may not be.