Black Tank showing full when it’s not. - Montana Owners Club

Lemmy · 07-13-2019, 07:30 AM

Our black tank is reading full even after it’s emptied. If the sensor is not reading correctly what is the best solution to remedy this issue? After searching the web I see lots of choices but do not know which one to start with.

MC

RoadRunnerTR21 · 07-13-2019, 07:59 AM

After you dumped the black tank, did you hook up a hose and perform a blank tank flush? Just make sure your blank tank valve is open when you are performing this operation. That might be all you need to do. If that doesn't work, more ideas will be forthcoming.

rslopez65 · 07-13-2019, 08:17 AM

We have never had one that worked and just don't care. Not sure why this seems to be so important. A small bit of TP dried on the sensor may cause a false reading. We know when we need to dump and do so without ever looking at the sensor. Personally, I wouldn't spend a lot of time worrying about it. You will surely get lots of tips on how to get it working again but I doubt you will find any permanent solution.

jeffba · 07-13-2019, 08:39 AM

When full the toilet will burp when flushing

**AZ Traveler** · 07-13-2019, 08:39 AM

Lemmy,

Take some black electricians tape and cover the black tank switch. The read out is totally useless unless you spend way too much time flushing the black tank after dumping it. Just dump your tank every 5-8 days depending on how many people you have in the rig.

**DQDick** · 07-13-2019, 09:21 AM

On the old rig I added outside the tank sensors and they worked great. The only problem was I had already established a dumping schedule to meet our usage and so never used them ever. Big waste of money.

Lemmy · 07-13-2019, 10:48 AM

We are about to do a tank flush hoping that fix’s the problem - thank you for all the quick responses we really appreciate it. All this can be very overwhelming as a newbie - which brings me to my next question should we keep gray and galley tanks open all the time when hooked up at a site ?

RoadRunnerTR21 · 07-13-2019, 10:57 AM

We leave the bathroom/shower gray tank valve closed and then dump when needed or after a black tank flush. The kitchen gray tank valve is left open while we are at our site. That's what we do but I'm sure you will get different opinions.

1retired06 · 07-13-2019, 11:01 AM

Our black tank sensors have never worked on any of our rigs. Have forgotten they are even there.

**DQDick** · 07-13-2019, 11:22 AM

We shut the grey tank valves a couple of days before we flush the black tank so we have water to wash out the sewer hose.

**Carl n Susan** · 07-13-2019, 12:08 PM

With a washer that drains to the shower tank, I have learned to leave that one open at all times. One never knows when management decides to do several loads of washing. The kitchen is open all the time as well. I ensure there is a loop on the sewer hose which acts as a P trap thereby blocking gasses and insects.

I flush the black tank until it runs clear after every dump. That also cleans the sewer hose.

Montajmahal · 07-13-2019, 12:32 PM

Quote:

Originally Posted by DQDick

We shut the grey tank valves a couple of days before we flush the black tank so we have water to wash out the sewer hose.

Exactly.

Also, what Carl N Susan said - if you have a washer definitely leave that tank valve open!

Lemmy · 07-13-2019, 02:08 PM

Yes we do have a washer so we have been making sure to keep it open while doing laundry . Thanks again for all the answers really helps to know we aren’t alone ��

WeBeFulltime · 07-13-2019, 02:43 PM

Quote:

Originally Posted by 1retired06

Our black tank sensors have never worked on any of our rigs. Have forgotten they are even there.

Same here. We are full time and never even look at them.

**Rondo** · 07-13-2019, 05:18 PM

Mark-- the tank sensors on all of the tanks except for possibly the fresh water tank are useless. Ours worked only the first week we had the new unit. They get TP on them and other items on the black tank and soap scum and etc on the gray tank probes and always give you a false reading. We keep our tanks all closed but have a routine of dumping the black tank and the grays about every 4 days or so. This makes sure the black tank's not building up and we use PLENTY of water when flushing the toilet also. We use a tank additive by the name of Happy Camper and it breaks down all that is in the black tank. While dumping the black tank I run the internal flush and when I think the tank is empty, I close the black tank valve and run the flush for about 5 minutes then open the valve again and empty the tank. I also have an external flush that I connect to the end of the sewer pipe that back flushes the tank again. Once that is done I close the black tank, open the galley gray, drain it, close that valve and open the shower gray and that cleans out the line and the sewer hose of any debri that might be in it. Close the shower gray and I'm done except for adding the additive down the toilet and dumping about 4-5 bowlfuls of water down into the black tank to make sure the black tank has some water in it and does not dry out.

CaptnJohn · 07-13-2019, 10:51 PM

Quote:

Originally Posted by carl n susan

With a washer that drains to the shower tank, I have learned to leave that one open at all times. One never knows when management decides to do several loads of washing. The kitchen is open all the time as well. I ensure there is a loop on the sewer hose which acts as a P trap thereby blocking gasses and insects.

I flush the black tank until it runs clear after every dump. That also cleans the sewer hose.

For some unknown reason the washer drains into the black tank of the 1/2 bath. Cannot leave that one open! I'm sure they have a reason. The only thing I can think of it is the closest other than the bathroom gray.

Dave W · 07-14-2019, 06:26 AM

On the last 5er I installed the Garnet SeeLevel external sensors that work great. They are not cheap. On this 5er I had to pull the belly cover for other reasons so decided to install the Horst (now Valterra) Miracle Probes. Oh well, $40 wasted bucks didn't hurt too bad. They are a little better but still virtually useless regarless of hype.

The best 'sensor' is your personal experience and knowing how long it takes to fill a tank, black or gray along with the occasional back flush with a hose end flusher - Camco or Valterra, which, IMO, is hands down better then the built in sprayer that kinda almost works.

richfaa · 07-14-2019, 09:09 AM

6 rv's and never had gauges that worked. We normally leave the grey and galley tanks open and always keep the black tank valve closed when at a full hook up site which we usually are.Dump the black tank and flush often.We dump every 3 or 4 days. We do not wait for that gross burp or let the black tank or for that matter any tank fill to capacity.

mazboy · 07-16-2019, 05:45 AM

They ALL show full after awhile. Just learn how to decide when to dump.

We can go several weeks for the two of us without any issues.

Or you can spend more money and have another more expensive sensor installed.

dmanhart · 01-26-2020, 10:46 AM

I'm reading this post with much interest because we just purchased a 2010 Montana. The black tank sensors indicate "1/3" immediately after dumping so I know they work relatively well. However, they show "full" after only a few flushes. We find it necessary to dump the black tank after only 20 flushes. This is very consistent - exactly 20 flushes.

I'm amazed that some are going 4 -5 days, some for several weeks, without dumping. The specs on this model 3455SA indicate a 50 gallon black tank but 20 flushes should not be more than 40 gal. Stool tank capacity is 1.8 gal. A new valve & stopper in the stool tank have been installed so water is not leaking thru the stool.

Any suggestions on what my problem might be ( other than being full of s___)?

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