Good questions all. Here is my "story", hopefully it'll explain a little better. And Unique is the brand that was recommended by the RV store I visited and the RV Proctologist guys who cleared the tank.
We've been full-timing for 7 years now, bought the rig new and just kept going. No dishwasher, No washer/dryer in the rig. Only 2 holding tanks, one black one grey. We take great pains to prevent as much food stuff and grease as possible from going down the drain. I have micro-screens in the sink traps, and a small shower drain catcher that keeps my DW's long hair from going down the drain. My hair's short, so no problem there. We have always used Dawn for hand washing our dishes and such.
I usually leave the grey valve open until just before the black tank gets full. I then close the grey valve until it and the black are full at the same time, then I drain the black and use the grey to clear out the drain hose, leaving the grey open until the next time. I don't see much gunk in the sewer hose when we move, so I think that has worked pretty well over the years. My black tank has a flusher installed so I use the hose to flush it out before I drain the grey. My grey tank does not have a flusher installed. I would have installed one myself, but the tank is inaccessible to me without completely removing it, so I never tried this.
As for this event, it "appears" (this means I have no proof) that over time, a layer of scum built up on the bottom of the tank. Soap, grease, whatever. It's impossible to keep all grease from going down the drain, pre-cleaning/wiping not withstanding. I also note that looking at my pipes exiting the holding tank, that there is about 3/8 to 1/2 an inch of space between the bottom of the tank and the bottom of the drain pipe. That means that anywhere between 3/8 and 1/2 inch of crud/water is always sitting in the tank. We sit for 3-4 months at a time, and travel in between. So it's probable that a layer has been building up in the tank.
According to the RV Proctologist, he's pretty sure this layer broke free and began floating. Maybe because of the AZ heat?? Then, when I opened the drain last time, the layer moved towards the drain pipe because of the flow and then covered the exit pipe. He described the layer as thick and plastic-like, and that's what the big chunks that came out were when he power blasted it. When I forced the hose into the tank, I was putting water underneath the "layer" and my hose pressure wasn't high enough to break through the layer.
That's pretty much it. So, what did I learn from this adventure?? The RV Proctologist told me the following:
1. Always leave the grey valve open when parked. Don't worry about using it to drain the hose.
2. When draining the black tank always make sure it is full before you begin. If you have to add water to fill it, do it. NEVER drain the black if it isn't full.
3. Attach a hose to the black tank flusher and turn the hose on just before you pull the valve handle to drain. The flusher will start swirling the water around as it drains, similar to a washing machine. That's the best way to help clean the black tank.
4. When travelling, drain and then fill both tanks about 1/3 and add a few tablespoons of Dawn soap to both tanks. The swishing action from driving will help keep the tank clear. When you re-park, fill and drain both tanks, leaving the grey valve open again.
5. About once every 3 months or so, or if you happen to park it for awhile, drain the tanks and fill to about 1/3. Add a cup of the Unique enzyme cleaner to both tanks and let it sit for a few days. If you're using the rig, it's ok to do this too. After a few days, fill both tanks and drain.
That's it. Oh, and he repeated: NEVER use Rid-X in your tanks, it will eat up the drain valve gaskets.
And finally, if your tanks ever get really gunked up, call the RV Proctologist in your area. They did a great job cleaning my tanks, a pressure washer is the only way to go.
Thanks again for all the thoughts and suggestions! I love you guys!!
Loren
