Black tank sensor always reads at least 1/3 full

myredracer · 07-26-2012, 10:14 AM

No matter what we try, the black tank always reads at least 1/3 full. Emptied it yesterday and it reads 2/3 full.

Have a Valterra elbow that I've used to flush from the outlet. Have used a wand down into the tank from the toilet. Also use chemicals every time and have tried the bag of ice trick. Nothing seems to work.

Is there anything we can do to get the sensor to operate properly? I have a feeling that it has read 1/3 from when we bought the TT last August. Maybe there's a fault with the sensor or readout?

tomjsas · 07-26-2012, 10:23 AM

Welcome to the faulty pooper sensor club. Seems most don't read correctly. I've had two trailers and neither one has been accurate. I've tried most of the tricks and about the only time it reads empty is if I've just finished using the built in black tank flush. But I can use the toilet a couple of times after that and it will usually jump right back up to 1/3 or more. Visually you will be able to see if the thing is full when you flush and for most weekend campers the 30 some gallon capacity of the black tank is way more than you will fill in that time (if you do fill it, well then you either have a huge family or you have a medical condition that needs attention

).

myredracer · 07-26-2012, 10:47 AM

Crap! Then maybe there is no magic answer to this perplexing issue....

Have I read that there is a sensor upgrade available out there?

Maybe they shouldn't bother putting in a sensor thus reducing the purchase price of an RV and they could just supply a dipstick instead?

Filthy Beast · 07-26-2012, 11:03 AM

I believe Herk installed the Horst miracle probes and did a nice write up with pictures and everything. You might try searching for Horst probes.

Dave_Monica · 07-26-2012, 11:14 AM

You soon learn the capacity of the black tank and then count by days. Ours is 38 gal capacity...with the 2 of us, we can go 12+ days before having to dump. If your toilet is a straight drop into the black tank (ours isn't), you can visually see the level. Personally, I wouldn't be worrying too much about the indicated level or bother spending money to try to make it more accurate.

Dave

stevengb · 07-26-2012, 11:16 AM

I don't believe I want to see the pics on that install !

cre10 · 07-26-2012, 11:23 AM

Quote:

Originally Posted by stevengb

I don't believe I want to see the pics on that install !

myredracer · 07-26-2012, 11:25 AM

Will look at the Horst probe and Herk's post (if I can find it) for fun at least.

This reminds me as a kid, when we spent every summer in a cabin with no sewer, water, power or phone. Had your basic outhouse. When the thing was full and the logs wouldn't go down, you knew it was time to dig a new one.

An RV toilet is sorta the same so I'm okay with the visual test.

RV Wizerd · 07-26-2012, 01:30 PM

Ok well if you know where you toilet is in conjunction to the out side discharge valve usually it should be located at that end.First does your toilet go directly into the tank via strait pipe or does it go via s pipe. If you have a strait pipe the wash out wand should do the trick as the probes are located to the right near the discharge valve but if you have a s pipe going to the tank that's another story in itself where cleaning it out will be more challenging. That's where a wash out sprayer adapt kit will do the job and can be installed relatively easy and can be purchased at a RV store.Also it sounds like you still have some solids that may have lodged themselves to the sensors , one key thing to keep in mined is that you must use plenty of water when doing #2 as some people don't use enough water to aid the breakdown of solids, and the solids have accumulated at the end of the tank, so you might try this is to fill your toilet up to the top and empty it into the tank 5to6times with the valve closed of course and take the trailer for a ride, the agitation of the water should free up the waste then empty the tank, you may have to repeat this two or three times.Once its clean remember that next time you go camping to start the black water tank off with a float of water that is fill your toilet four or five times before use.

Dave_Monica · 07-26-2012, 01:38 PM

Quote:

Originally Posted by RV Wizerd

if you have a s pipe going to the tank that's another story in itself where cleaning it out will be more challenging.

Hmmm...I've never heard of a S trap installed on a RV toilet.

Dave

myredracer · 07-26-2012, 01:47 PM

Thanks Wizerd, that's some good info.

Our toilet drops straight down into the tank so we can see what's down there and get the wand in okay. I've been wondering just what the sensor looks like - maybe a pair of wires that sense the change in resistivity? I've thought about installing one of the rinse devices on the side of the tank ("tornado"?).

Have tried filling the tank as high as I thought feasible and letting it soak before dumping. I can see how it is tempting not to flush with adequate water to try and save on filling the tank up too soon but that can worsen the sensor problem. I wonder if it would help to fill the tank up with a bit of water before you let solids drop into it?

Dave_Monica · 07-26-2012, 01:57 PM

Before heading to the dump station, I empty some of the grey water into a bucket and pour into the toilet to fill the black tank ...more water will help empty it completely. I also use the blackflush until reasonably clean on the clear elbow I install before the waste hose.

Last step is to pour a cap of detergent and 1/2 cup of Calgon water softener along with 6 gal of water down the toilet to slosh alround on the way home. Yes, you lose some capacity but it keeps the black tank cleaner.

Dave

**Herk7769** · 07-26-2012, 02:04 PM

http://www.forestriverforums.com/for...ion-16089.html

Would actually be worth your time.

myredracer · 07-26-2012, 02:05 PM

Thanks Dave. Will try the detergent idea for a trip home. Is the Calgon because you have hard water there? Ours is typically soft on the west coast except for our well water at home.

I have to think that the toilet paper messes up a sensor? The RV stuff seems to be pretty good at adhering to all kinds of surfaces......

myredracer · 07-26-2012, 02:08 PM

And thank you Herk for that info. According to the little bit I've read on the 'net so far, it seems like all you do is install the new sensor and retain the existing readout and wiring. Have not found a price yet. If not too pricey, might be a great upgrade project.

**Herk7769** · 07-26-2012, 02:08 PM

More info on your problem.

http://www.forestriverforums.com/for...tor-26746.html

Dave_Monica · 07-26-2012, 02:11 PM

Quote:

Originally Posted by myredracer

Is the Calgon because you have hard water there? Ours is typically soft on the west coast except for our well water at home.

The detergent and calgon are to coat the insides of the black tank so that material doesn't stick as readily. It's referred to as the 'GEO Method'.

Dave

**Herk7769** · 07-26-2012, 02:13 PM

I found they were very inexpensive and work great. Although I am currently troubleshooting a gray tank "full" problem right now, I believe the DW dumped some grease into the tank. Grrrr...

I bought a gallon of ZEP Purple and will let you know how it works. I talked to the inventor of the Horst probes and they are made of Teflon and stainless steel. The ZEP degreaser should solve my problem.

**Herk7769** · 07-26-2012, 02:15 PM

Quote:

Originally Posted by myredracer

I have to think that the toilet paper messes up a sensor? The RV stuff seems to be pretty good at adhering to all kinds of surfaces......

I have found the "TP on the sensor" a myth. The OEM probe is a stub and what sticks to it also sticks to the wall creating a resistance path to the ground sensor. It only needs to be 40K ohms to turn on the "FULL" light.

papap · 07-26-2012, 02:21 PM

29$ for grey, 34 for black.

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