Black water tank doesn't drain

[ForrestAZ]

I just came back from a campground with full hookup. When I left, I didn't check the monitor panel, assuming everything had drained properly. Upon getting home and cleaning up, I noticed the monitor shows the gray tank is empty but the black water is 2/3 full. Opening the drain valve, I got about a gallon of black water and then nothing, although the monitor still shows the tank 2/3 full.

I don't know why it would be clogged, and I have no reason to doubt the monitor. I put in the standard RV tank chemicals upon getting home, but they haven't helped. I'm reluctant to put in household drain cleaner. Any suggestions how to empty the tank?


Jay Flight 154BH

[Robbbyr]

Originally Posted by ForrestAZ

I just came back from a campground with full hookup. When I left, I didn't check the monitor panel, assuming everything had drained properly. Upon getting home and cleaning up, I noticed the monitor shows the gray tank is empty but the black water is 2/3 full. Opening the drain valve, I got about a gallon of black water and then nothing, although the monitor still shows the tank 2/3 full.

I don't know why it would be clogged, and I have no reason to doubt the monitor. I put in the standard RV tank chemicals upon getting home, but they haven't helped. I'm reluctant to put in household drain cleaner. Any suggestions how to empty the tank?


Jay Flight 154BH

Are you sure it isn't empty? The regular tank monitors supplied on most RVs are notoriously unreliable. Very common for black tank especially due to fouling of the sensor probes.

Does your unit have a black tank flush? If so, hook up to a dump site and connect a hose to the flush connection and see if after a bit of flushing you get water coming out of the tank. If no flush, get a pail of water and dump it down the toilet and see if it immediately flows out of rig.

[MrJeep]

I agree with Robbbyr, I've had three different TT's and none of the black tank monitors were accurate.

[JFlightRisk]

And I wouldn't put drain cleaner in it. Too harsh of a chemical.

[CAG]

Originally Posted by ForrestAZ

I just came back from a campground with full hookup. When I left, I didn't check the monitor panel, assuming everything had drained properly. Upon getting home and cleaning up, I noticed the monitor shows the gray tank is empty but the black water is 2/3 full. Opening the drain valve, I got about a gallon of black water and then nothing, although the monitor still shows the tank 2/3 full.

I don't know why it would be clogged, and I have no reason to doubt the monitor. I put in the standard RV tank chemicals upon getting home, but they haven't helped. I'm reluctant to put in household drain cleaner. Any suggestions how to empty the tank?


Jay Flight 154BH

Poop pyramid. You need a flush wand to run down the toilet or back up the flush drain. The first is going to be easier. You can buy one or make your own out of 1/2 Pex line, and a hose connection with shutoff.



Chemicals are not going to help at this point. The tank will need to be power flushed and to avoid this in the future, lots and lots of water with each toilet used. Then dump often.

[RogerR]

Add some dawn , maybe 1/4 cup plus some water softener maybe 1 cup Calgon plus 2/3 full of water. Then drive around to slosh it around may start the flow. But the wand cleanout will be needed to finish the job completely.

You can also send a running hose backward up the drain pipe may work.

[Route 66 Traveler]

Originally Posted by ForrestAZ

I don't know why it would be clogged, and I have no reason to doubt the monitor. I put in the standard RV tank chemicals upon getting home, but they haven't helped. I'm reluctant to put in household drain cleaner. Any suggestions how to empty the tank? Jay Flight 154BH

Have you visually looked down the toilet with flashlight and with the water turned off to verify if it indeed is full? You might be surprised to see the bottom of the tank which tells you your sensor isn’t working correctly…a very common problem.

If it is indeed full of liquid get a cap for your sewer connection that has a hose connection, the back flush a few gallons to dislodge the blockage. Many times excessive use of TP, or using the wrong type, will easily clog the the sewer pipe.

[ForrestAZ]

Great suggestions. Good to know the sensors can get fouled. I haven't had this issue before, so have not questioned the monitor. I'll start by dumping some more water in the toilet and see if it comes out. I had put some Dawn in the bucket I ran through already, so appreciate the supplementals. Then I'll go for the wand approach. Had considered feeding water back into the drain, and may try that if all else fails. I appreciate everybody's comments.

[Route 66 Traveler]

Here’s the adapter I use to back flush. The open end need to be capped.

https://www.amazon.com/Valterra-F02-...%2C159&sr=8-31

[stinger608]

Something else that hasn't been mentioned; when in a full hookup campground, you should leave the black tank drain closed until it's about 2/3rds full.

This will, usually, stop any plug up issues and "poop pyramid" from occurring.

[ARoamer]

[QUOTE=ForrestAZ;1115295 I have no reason to doubt the monitor.
Jay Flight 154BH[/QUOTE]

The OEM tank monitors are not reliable. If your tanks are exposed underneath, crawl under and give them a push or knock with your hand and compare results with the known empty grey tank.

[norty1]

When you empty your tanks for the last time after a camping trip, add at least 4-5 gallons of water to the black and grey tanks before you head home. Also some water softener if you want to. Let that slosh around and I just leave it there until I get to my next cg., even if it sits at home for a couple of weeks or longer the water will keep anything from drying out had it will prevent future troubles with draining.

Forget the tank monitor gauges, It will relieve you of a lot of grief trying to make what they provide accurate.

One more tip that helps us, we leave a roof vent slightly open when traveling and it helps vent any odors that may be inside as you travel.

[Kevin Cooper]

Much of the time the reason that the tank monitor pins do not work is because of struvite. It is a crystal formed by magnesium(from hard water), phosphate (major element of poo), and ammonia(from pee) in equal parts. The crystals stick to the walls of the tank. When wet along the sides, the sensor buttons are fooled by the moisture in the struvite. So do as one suggested earlier to clean your tank, but I use different formula. I use 1 cup of Borax dissolved in gallon of hot water, and either clothes washing or dish detergent. The detergent cleans the surfaces of the tank, and Borax or Calgon soften the water cutting off the magnesium needed to form crystals. Fill tank 1/3 full and go on next trip. Leave it in, until dump time. After a few times your sensors will work. The detergent is optional after that. I always use the Borax. Also, never use bar soap in the shower or sinks. Use liquid soap (really not soap, detergent) no soap scum.

[ForrestAZ]

Thanks for this detailed info. I am out of borax now but am adding it to my shopping list and will do this procedure shortly.

[Kevin Cooper]

First tank should get lots of nasty stuff out. I use a flush king to make sure I get everything out. It really helps.

[jetlag]

Originally Posted by Kevin Cooper

Much of the time the reason that the tank monitor pins do not work is because of struvite. It is a crystal formed by magnesium(from hard water), phosphate (major element of poo), and ammonia(from pee) in equal parts. The crystals stick to the walls of the tank. When wet along the sides, the sensor buttons are fooled by the moisture in the struvite. So do as one suggested earlier to clean your tank, but I use different formula. I use 1 cup of Borax dissolved in gallon of hot water, and either clothes washing or dish detergent. The detergent cleans the surfaces of the tank, and Borax or Calgon soften the water cutting off the magnesium needed to form crystals. Fill tank 1/3 full and go on next trip. Leave it in, until dump time. After a few times your sensors will work. The detergent is optional after that. I always use the Borax. Also, never use bar soap in the shower or sinks. Use liquid soap (really not soap, detergent) no soap scum.

X2 on the Borax

[Markb5900]

We had to drop the belly cover on mine for a different issue, but when we did I looked where the sensors were. The factory put the 3/3rd set right near the opening to empty the tank. If I have 2 or so gallons in it, it reads 2/3 full or a piece of toilet paper gets on it.
Just something to look at.

[Kevin Cooper]

Originally Posted by Markb5900

We had to drop the belly cover on mine for a different issue, but when we did I looked where the sensors were. The factory put the 3/3rd set right near the opening to empty the tank. If I have 2 or so gallons in it, it reads 2/3 full or a piece of toilet paper gets on it.
Just something to look at.

So, it was wired incorrectly.

[Markb5900]

Not wired wrong, but sensor placement was ignorant.

[Kevin Cooper]

Originally Posted by Markb5900

Not wired wrong, but sensor placement was ignorant.

Oh ok. My son lives in Jefferson City. We camped East and West of city.
Best wishes!