Originally Posted by 1996VOGUE
what does the waste water flush do ?
1996; there is a LOT written on the black and gray water flush, with some "how to" videos available too. And everyone has their own twist on the process, so read it all and think about what works for you. I'll share my procedure here, which has worked great for us for the past few years on two separate RV's, both of which we purchased new.
USING the toilets: We have found most of the drop-in types of additives work pretty much the same, and we do use them. Some of them say they are for "weekends" and others say they are good for "up to 7 days." I tend to plop one in every 3 days regardless. They are meant to provide a more pleasant odor, and they claim to help break down solids and tissue.
In addition to this, every so often I add about a cap full of liquid Calgon, plus a cap full of cheap liquid laundry detergent to a gallon or so of water. I pour this mixture down my toilet AFTER I have dumped the tanks thoroughly (see below), and I before I head home or to my next destination. This is loosly called the "geo method" (there are variants to this) but essentially this kind of cleans the side walls of the tanks, and it makes them more slippery so stuff doesn't tend to stick to the inside walls as much. I do this about every 3rd or 4th weekend of use--not every time. Some people ONLY use this and skip the chemicals.
In both of my RV's, if someone flushes the toilet while the bathroom fan is running, they regret it. The fan is strong enough to suck the air out of the black tank and fill the bathroom with terrible odors. So... fan off, then flush. No exceptions to that one for us!
Finally--flush with lots of water. We discovered that our toilet flush pedal has an "up" position too, that was not mentioned to us during our walk through. If you pull up on the handle, it fills the bowl with water but doesn't dump it. This is a nice way to pre-fill the bowl for the next person... and it helps assure that there is plenty of water to dilute urine and float the solids (see below).
SETUP WHILE CAMPING:
This is the most common area where newbies make mistakes. When you set up camp, it is perfectly fine to hook up your sewer hose from your RV to the campground sewer, and if you want, you can open the GRAY valve so that shower water and kitchen sink water can go down the drain, into your gray tank, and straight into campground sewer.
Whatever you do... DO NOT open the black tank valve at this time! You want the solids from the toilet to be swimming in lots and lots of water in your black tank. Every flush provides water (hold down the flush handle longer than you think to add more water). But if you open the black tank while camping, the water will exit the black tank, but the solids usually will just sit there. Eventually, this builds up into what some call the dreaded pyramid of death! Use your imagination... not a pretty thing. If the solids sit in the tank for long, they become difficult to remove. So only open the black valve when you are flushing the black tank (see below).
DUMPING THE TANKS:
My RV's have both had a garden hose connector for flushing the black tank. You can connect a garden hose to this and turn on the water supply. It sprays water into the black tank from a wand that spins around and around at the top of the black tank--kind of like the wand in the bottom of your dishwasher. Now... I turn on this hose EVERY time I dump my black tank. I usually dump my black tank when it's about 1/2 full (that's just how much we use it in a typical weekend), but I use this hose to fill up the black tank to about 3/4 or so. This involves turning on that water hose, then going inside my RV to frequently check the tank levels until I get to 3/4 full. Then I run out and pull the lever to dump the black tank.
I have a clear piece of sewer line connected between my RV and my sewer hose, so I can see what comes out. It's gross the first time you do it., to which I told myself to "Suck it up buttercup," cause that grossness is a good thing. It lets you know if you need to refill the black tank and dump it again. Typically the water clears up quite a bit after the initial surge, and sometimes by the end of the dump, the water is already clear. Sometimes I fill the black tank a second time--this time maybe only to 1/4 or 1/2 full, and that always returns clear-looking water.
NEXT... I close down the lever to my black tank and open up the lever that dumps my gray tank. This is just sink and shower water, but it can get smelly from grease or other food particles that you put down your kitchen sink. Usually it's just cloudy in color. There is no outside "fill" hose for this tank, and I never do anything other than to dump my gray tank. (I do pour some of the calgon/soap mixture into my kitchen sink when I do my black tank--which keeps the gray tank slippery and cleaner.)
These procedures have worked well for me. My tank meters are the original type that most RV builders uses, where you push the button and the sensors trigger red LED lights that indicate empty, 1/4, 1/2, 3/4, or full. These sensors on our first RV occasionally got dirty and would give a false read (tank wasn't 1/2 full, but it would read 1/2 full). That was when I read about the calgon treatment, and since starting that treatment, my LED's stopped the false alarm in the last RV, and have never triggered a false read in the new one.
Hope this helps. I know it's a little graphic, but hey, we're all adults here, and everyone poops!