Black tank always 2/3 full.

**hampal** · 05-25-2021, 01:03 PM

We've had our Imagine 2500 RL for 1 year now. I've tried rinsing the black tank for up to 10 minutes but the level always shows as 2/3 full. I rinsed it this past weekend for 10 minutes with a line of trailers at the dump station behind me until I felt I couldnt tie up the dump station any longer. The water was clear coming out when I stopped. I let it finish draining but the indicator still says 2/3 full. I know its a common problem. Is it something I just have to live with?

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**huntr70** · 05-25-2021, 01:04 PM

Pretty common issue.

They are resistance sensors, so most likely just "something: hanging on the probe in the tank.

You could try traveling with a bunch of clean water in the tank and add a small bag of ice before traveling. It seems to scour the sensors.

**hampal** · 05-25-2021, 01:23 PM

I'll give it a try. Thanks.

How much clean water should I put in the tank? IIRC the capacity is 45 gallons.

**Ynot4me2** · 05-25-2021, 02:44 PM

I'd go about 1/3.
You should also look into using the Geo Method. Check this article out https://kleentank.com/the-geo-method/

Sent from my SM-P610 using Tapatalk

**AZMike** · 05-25-2021, 05:39 PM

This works very well.

https://www.amazon.com/dp/B000BUQOCC...roduct_details

**sande005** · 05-25-2021, 10:02 PM

I make sure my last night camping is at a full hookup campground.
First I dump.
Then close the valve, and run the rinse for 3 min. (I timed it when new, so know that that comes no where near filling the tank). Open and drain.
I'll repeat until not even little bits come out. Sometimes alternating with turning the rinse off completely, or letting the rinse run for a while with the valve open.
It can take 20 min. to 45 min of playing with the above to get it all out.
THEN my tank will read empty.

Of course, it then gets stuck at 2/3rd on the next trip out on about the 3rd day, and stays there until I again do a "super clean out".

**Sportsdad60** · 05-26-2021, 05:12 AM

Geo method works for us. I do it twice a year (When we leave for texas, and when we return in the spring)
https://www.youtube.com/watch?v=0M08l9lYs1A

**HighFive** · 05-26-2021, 05:32 AM

I have not had a issue with the black tank sensor. One of the things I do which I believe helps keep the tank and sensor clean is to use all full flow connectors, pressure regulator and a 5/8 hose to get maximum water volume to the spray head in the black tank clean out. Most of the hose y connectors with shut off valves and pressure regulators have small orifices which limit the water volume. I use this pressure regulator. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 It may be in my head but I do see more water flowing out the waste water outlet then before I went to all full flow.

**finz04** · 05-26-2021, 05:39 AM

Tank sensors can be notoriously unreliable. I'm not an RV tech (nor do I play one on TV), so I don't know the particular reasons why, just that it's been my experience.

The tank flush is a nice feature and I'd rather have it than not have it. But it's moderately effective for "cleaning" a tank. What seems to be most effective for me is to run the flush with the black tank closed. I time it to run for 3 minutes (and never, never walk away and leave it unattended). Then I open the valve and that sudden rush of water will better move stuff out of the tank.

Most of the chemicals are pretty good at what they do. Also good is an occasional bottle of fabric softener with a 1/2 tank of water (or let your flush run for about 2 minutes or so) in the black tank (not the greys or fresh water) when traveling. It doesn't digest or breakdown anything but it can soften and loosen some of the toilet paper which might be clinging to the inside of the tank including a sensor which allows them to move out with the next flush.

But it also just might be that no matter how clean things are it may not read as empty on your board.

**WhittleBurner** · 05-26-2021, 08:52 AM

Originally Posted by finz04

Tank sensors can be notoriously unreliable. I'm not an RV tech (nor do I play one on TV), so I don't know the particular reasons why, just that it's been my experience.

The tank flush is a nice feature and I'd rather have it than not have it. But it's moderately effective for "cleaning" a tank. What seems to be most effective for me is to run the flush with the black tank closed. I time it to run for 3 minutes (and never, never walk away and leave it unattended). Then I open the valve and that sudden rush of water will better move stuff out of the tank.

Most of the chemicals are pretty good at what they do. Also good is an occasional bottle of fabric softener with a 1/2 tank of water (or let your flush run for about 2 minutes or so) in the black tank (not the greys or fresh water) when traveling. It doesn't digest or breakdown anything but it can soften and loosen some of the toilet paper which might be clinging to the inside of the tank including a sensor which allows them to move out with the next flush.

But it also just might be that no matter how clean things are it may not read as empty on your board.

I agree with running the flush with the valve closed only II run it for 8 minutes. I had tied it once when the gauge was working. After 10 minutes it was a little more than 3/4 full. At 8 minutes I thought I would be safe about not going to far. I will do that over and over till there is nothing but clear water coming out. takes at least 4 tiimes and quite often a lot more.