Tuesday, April 13, 2010

RV Basics : Black Water or Sewer System Information

We have yet another little mystery with Puma. The black water indicator is STUCK at 2/3 full and there is very little we can seem to do to get it unstuck. Well I haven't gotten it unstuck, but I will tell you some things that I've learned.

My first observation is that as near as I can tell, the sensors for the black water are a pretty common problem.

My first question is what do the black water holding tanks look like? I found a page that has many pictures of the black water holding tanks and I think this is probably very representative of what most black water or sewer holding tanks look like.

On our PUMA, I can't say for sure, but I'm pretty sure that the tank monitoring unit is from KIB and what I'm showing is an almost perfect copy of our unit :

From RV Park Review videos, RV basics, and travel stories with Sheri and Marlan

I found the following wiring diagram on the kib web site. You can get a PDF, but I show just the section that shows the wiring of the black water (sewer) tank sensor system :
From RV Park Review videos, RV basics, and travel stories with Sheri and Marlan
(I'm hoping you can blow it up by clicking on it) .

How the sensor system seems to work : It looks like this is as simple as a wiring system that has a ground and then three wires at different levels in the tank. When the "lovely goo" level raises in the tank, it contacts a wire and then reads a lower resistance than when the substance isn't in contact with the wire. This seems notoriously unreliable. But now I have something I can work with to see if the sensor is just covered up or broken.

Alternative ways of sensing tank levels : I also think there are other methods like capacitive sensing, RF sensing, ultrasonice sensing (requires being in the tank) as well as the resistive. A quick search on the web yields several systems quite easily. 

One other thing we're going to do is to start using a little water softener in our black tank. It doesn't look harmful and it is supposed to make your tank 'slickery' which helps the debris sluice on out. This is called the geo method, or at least part of it for sure. We don't want to use many chemicals, but we thought water softener seems like a simple/good idea. This article isn't about black water tank care, but just about simple facts about black water tanks. I have found that there just isn't info ABOUT the tanks, but there is lots about caring for the tanks. 

No comments: