How to Clean the Black Water Tank
First, dump and flush as normal -- no detergents and PLENTY of water. Once that's done, open your grey tank and flush the hose with the grey water, then close dump valve. Rinse and open the dump valve. Continue to repeat the process until clear water comes out. Close the dump valve and move on to the next step.
Many Tiffin RV’s are now equipped with a hose connection that will allow you to fill the black tank with a water spray. This is a gigantic improvement over the old way of using a hose wand injected inside the toilet.
How To Freshen Your Black Tank:
Now comes the easy part. Pour about a quarter cup of ordinary dishwashing detergent in the tank (NON anti-bacterial version), "Dawn" or "Joy" are best. Then pour in about two gal of water. Drive RV to nearest market, diesel stop, or convenience store. Get about two or three bags of ice cubes and pour them in tank (down the toilet). Then drive to RV park or similar -- make a holiday of it -- (about a two to four-hour drive is adequate). The tank will be about as clean as it ever gets as the ice cubes slosh around and scrub it. Get a site with full hookup. Dump and flush repeatedly. Add about three gallons of water when done. Remember that (Bio needs something to work on). Add bio per container instructions, then drive home, or wherever your next stop is, to mix things thoroughly.
Routine future dumping should include simple flushing with water and no detergents (unless doing the whole process all over again). You want to keep a residue of the good bio going. (Kind of like a sourdough starter.) Do all this properly, adjusting amount of bio through experience, and you should be trouble free. In my case, as an example: With a 40 gal tank, using "Eco-Save," I put in only one (liquid) capful or one tablespoon of dry version every-other dump (or more) and am odor free and don't have any "floaters" in the tank.
One last point: If you accidentally have a spill of sorts while dumping at a dump station, for heck sakes clean it up. Please don’t leave it for the next person. Usually it only takes a few minutes to rinse the area down with fresh water into the drain.
Tip: Buy a box of surgical gloves and wear a set when performing this duty. Eliminate the chance for spreading any type of disease by simply disposing of the throw away gloves prior to getting back into the motorhome.
I also carry a spray can of Lysol in the dump area and upon completion, I spray all of the hose ends, etc. with a generous amount of spray, Including my hands. I then wash them prior to getting back in the motorhome.
REMINDERS AND ODDS AND ENDS
* Neither black or gray water should stink IF you treat them properly. You SHOULD NOT just cram chemicals in a tank. You use "biological" agents that decompose waste.
SIMPLE SEWAGE TRICKS
• Keep jars with screw-top caps for disposing of things like cooking grease, alcohol, paint thinner, etc.
• Don't use colored, double thickness, perfumed, household toilet paper because it just makes sludge and doesn't biodegrade fast enough. But don't bother with RV toilet paper that costs too much either. Generic, single-layer, el-cheapo toilet paper is the same thing as RV paper and lots cheaper. Better, in my opinion, is "Scott" brand single-ply, white, unscented toilet tissue sold in supermarkets in 1,000 sheet rolls. feel like it).
• Supervise children and visitors! Kids will throw anything into the toilet just to see where it goes (and they'll hold the pedal down an hour to do so and you'll wonder why you ran out of fresh water and wonder why you have to dump after a one-day drive). Non-RVer visitors will throw diapers, sanitary napkins, cigarette butts, apple cores, peach pits, facial tissue--(you name it) in your john without ever thinking about it--just like they do at home.
• Read the label on cleaning agents. Don't use caustics; use biodegradables. Baking soda (or Bon-Ami) is every bit as good a cleanser as the poisonous stuff.
• Baking soda is also an excellent drain cleaner. Pour a cup into sink/bath drains at night (just before bed), pour a cup of water on it (just enough to get it down in the P trap), leave it 'till morning. You don't have to flush it away with copious amounts of water either. It won't hurt a thing.
• Remove your black and gray sewer caps once in a while. Clean them and put a very thin coat of grease on the "O" ring seals and you won't be dribbling sewage all over the country (or next to your neighbor). "Plumbers Heat-Pruf" grease is best, but "white" grease is good too. "Vaseline" works but tends to get sticky.
• A piece of wire coat hanger a foot or so long with about ½" at the end bent 90º is a good tool for cleaning the "slots" in slider valves and some toilet valves. (Don't drop the thing in the toilet!)
• Don't ever stick anything down in the toilet bowl unless you have a string tied to it! The retrieving of brushes, flashlights, etc., from the black tank is called "diving for pearls" -- but it ain't near as much fun.
Use all the water saving tricks when out in the boonies, but, when on a full hookup, use water lavishly (just for a time, not forever). You'll have nice, clean tanks and hoses. But don't use someone's full hookup as a place to dump poison into their septic tank.
• (I shouldn't put this in here, but I can't resist it) There's an old RVer joke: If you're ever faced with an insurmountable poop problem, consider getting an "Airstream" -- because, as any Airstream owner will tell you, "theirs don't stink."
• Think about what you're doing when dumping your black tank. Screw up many of the above, when you're half potted or distracted by BS-ing with your neighbor, will end up with your neighbors in hysterics and you with 40 gallons of poop on your shoes.
Saw this happen one time. I thought it was hilarious, but the guy with the mess sure didn’t.
Submitted by Mike Sundberg - 3/16/06