Dumping Black Tank RV

Dumping and the Black Tank

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Dumping and the Black Tank

A typical Black Tank problem reads something like this "my RV has developed a problem with the toilet being plugged. I cleaned one clog and changed brand of paper and now I have another clog. Any ideas out there?

Several things may be going on, so let's discuss some of the more likely possibilities.

Toilet paper: You should be using a single ply toilet paper..........because a single ply toilet paper will easily dissolve in water. If you are using one of those soft multiply toilet papers it may not be breaking down. Purchase some Scot's single ply toilet paper and put it in a glass of water. Compare that with what you use at home. It should tell you what you need to know. If you do not want to spend time performing the test I can tell you that the expensive TOILET PAPER will still be there looking like a piece of TOILET PAPER at the end of a week. Shake the glass of water sloshing it around and it still holds the shape of TOILET PAPER That piece of CHEAP Scot's single ply TOILET PAPER from your local grocery store completely dissolves almost like sugar or salt. The point being: One can and will clog a system while the other will not. It is your choice.

Quantity of TOILET PAPER used: Some have pointed out that they have problems when a group of females utilize the RV-toilet because they tend to utilize more TOILET PAPER If this is the case your black tank is going to need more liquid added to the mix to make things fluid enough to flow. The simple solution is to put more water in the toilet before flushing. The type of TOILET PAPER used can also be a problem if is used in bulk, remember your RV isn't flushing a gallon or more of water into the tank with every flush like your home toilet. If your guests are going to be using copious quantities of TOILET PAPER then you are going to have to introduce an equally copious quantity of water to the tank this is especially true if you are using multiply TOILET PAPER that is not disintegrating.

Volume of water in Black Tank: Some RV's only have the toilet emptying into the Black Tank while others have both the toilet and bathroom sink emptying into it. Those with the bathroom sink plumbed into the black tank will put more liquid into the tank and thus are LESS likely to have a clogging problem. Those with just a toilet emptying into the black tank stand a MUCH greater chance of not having enough LIQUID entering the black tank to adequately flush when it is dumped. Determine which tank your bathroom sink is plumbed to. If it is plumbed to your black tank you should be getting sufficient liquid in your black tank provided you are using single-ply TOILET PAPER

The black tank needs liquid in order to "flush/dump" properly. Make sure that your are supplying adequate liquid to the black tank. And use one ply-toilet paper

Let me share a TRUE story with you. Yes this story really happened and it happened just this way. We were dry camping in Grand Teton National Park one summer. We always camp in Gros Ventre Campground which is in Grand Teton NP but also very close to Jackson, Wyoming. It is a large campground with a central dump station. We were at the dump station one day doing our standard 10-day routine of dumping the holding tanks and filling up with fresh water. Another RV was also in the central dump station at the same time. It was a nice, fairly new diesel pusher. The man in his 50's was traveling with his 3-teen age children. I think they were boys but could not be certain as they all had long hair and wore clothes that did not flatter gender if you get my drift. Anyway, the man was asking me for help because "something ain't right". He said he was sure his black tank was full but nothing came out when he pulled the black tank dump valve. I assured him that I completely and thoroughly understood the operation of his black tank and dumping system and that I would help him. First, how did he know that the black tank was FULL if nothing was coming out when he opened the black tank dump valve? "Well duh" he said, because the toilet is full of stuff and will not flush. I scratched my head as that was hard for me to believe. However, before going inside I got down and operated the black tank valve for myself to assure that in fact the black tank valve was indeed opening. It was indeed operating properly. Now it was time to go inside and see the full toilet that would not flush. Sure enough when we got inside, and he opened the lid on the toilet, it was indeed full and not looking pretty at all. At this point my mind was telling me that the flush valve on the toilet was not operating so I checked it myself. In order for me to check that I had to turn off the water to his toilet because it could not hold any more water and as you know when you operate the toilet valve water flows. Now, with the water off I operated the toilet flush valve. I could feel it mechanically moving but absolutely NOTHING happened when the toilet flush valve was open. What the HELL? When the toilet flush valve is OPEN there is nothing but a 4" pipe dropping straight into the black tank. There is NO WAY that can be stopped up. This thing is not draining anything out of the toilet with the dump valve being held open. This is totally unbelievable, as in beyond comprehension. I had the man take a cup and dip some of the water out of the toilet into a bucket so we could have some room to work. He actually dipped and dipped until there was virtually no liquid left in the toilet. All that we could see at the bottom of the toilet as it entered that 4" black pipe to the black tank was toilet paper. We had gotten down far enough to see the toilet flush valve open and close but immediately below that dump valve was nothing but toilet paper. The man got me a coat hanger. I straightened it out and started poking at that mass of toilet paper. It was fairly solid but I kept poking and we added some water from the sink to loosen the toilet paper lodged in the black pipe. Eventually, over 5 to 10-minutes we got through that mass of toilet paper and things started working again.

The problem was caused by his children, all in their mid-teans) using massive amounts of toilet paper with little or no water. They used so much that it seriously clogged the large black pipe leading from the toilet to the black tank. I would have said it was impossible but I saw it with my own eyes. There was nothing in the clog other than tightly packed toilet paper. Now mind you it was good quality toilet paper, as in the multiply that does not dissolve well in water. I am positive that the multiply paper played a role in this clog. I am also positive that not using enough water to properly flush played a major role in this clog.

There are TWO things you can take away from this. Number one, it is better to use one ply toilet paper because it easily dissolves in water. I know we all like multiply toilet paper but seriously it is better to use one ply in your RV. Remember that you do not want undissolved toilet paper to get clogged in the seal of your dump valve. Multiply toilet paper that does not dissolve good can and often will get clogged in the dump valve which is a knife valve with a large grooved seal that the edges of that knife valve or slide valve slides into. The second thing thing to take away from this is the need for plenty of water in the flushing process. Remember, that what goes into the black tank has to flush out when you open your dump valve. It will not flush properly if it does not have enough water to adequately flush all the solids out. If you have adequate water in the black tank the liquid will easily carry the solids out.

Chemicals---are they necessary?

That is a question strongly debated by knowledgeable individuals. Some individuals, myself included, do not use any chemicals in our tank. Others would not think of not using chemicals.

States and Municipalities are getting concerned about the chemicals being introduced into septic/sewage systems. The following was posted on an online forum: I was told at an FMCA gathering last weekend that California campgrounds (maybe only in certain areas) are being fined if they find a hint of formaldehyde in their septic systems. One CG the folks stopped at asked them to bring the stuff they use in their tanks into the office with them to register. They asked what would have happened if the product they produced had contained formaldehyde. The response: We would have invited you to stay but prohibited you from dumping into our system.

More and more RV parks are insisting that their customers NOT use formaldehyde based chemicals. For those that must introduce some sort of product to their black tank there are bacteria based products. These bacteria based products are available as liquids or solids.

For those that scoff at such an idea here is the result of chemicals used in black tanks. What I am about to present was taken from the Borrego Palm Canyon State Park web site: http://parks.ca.gov/default.asp?page_id=638

For those of you than are not familiar with Borrego Palm Canyon SP it is located in California about 100-miles south of Palm Springs.


NEW Hook-up Site Procedures

As of March 29, 2007 the Dump Station at Borrego Palm Canyon Campground is closed until further notice. Testing required by the State Water Resources Control Board has detected above normal levels of Total Nitrogen, which has the potential to contaminate groundwater.

The primary cause for the elevated level of Nitrogen found in this dump station is directly related to the presence of two chemicals that are
routinely used in the black water tanks of most RV's, they are: Para dichlorobenzene (used as a insecticidal fumigant against clothes moths
and as a deodorant for garbage and restrooms) and Para formaldehyde (traditionally used as a disinfectant, sanitizer, fungicide and microbicide).

In order to comply with the State Water Resources Control Board requirements, we now require all RV holding tanks be emptied before arrival to the campground. Campers arriving with full holding tanks will be redirected to a local dump station to empty their tanks before returning to occupy a site in our Hookup Area. While in the campground, park visitors shall not use deodorizing, or sanitizing products, which contain Para dichlorobenzene or Para formaldehyde.

As you can see from this bit of information the problem is real, not just the figment of someone's imagination.

Again, myself and a host of other seasoned RV'ers do not add anything to our tanks. Here is what I do and why:

I do not put any chemicals in my tank. I do not rinse out my tank. All I do is pull the handle and dump then close the valve after the "big-rush". I do not just let the black valve stay open until EVERYTHING is drained. By not draining everything out of the black tank I am leaving a few gallons of active bacteria culture ready for the next load. Others DRAIN everything out of the black tank, rinse the tank thoroughly, then add several gallons of fresh water and some fresh bacteria starter purchased from WalMart.

Note that I am accomplishing the same thing by leaving some liquid "starter" in the bottom in the of the tank. It is your choice how you do it.

Where some add chemicals, I leave some bacteria culture to work its magic on the incoming stuff. I firmly believe, KNOW, that bacteria breaks down solids in the black tank thus making the dumping process much simpler. ---- And simpler, at least for me is BETTER.

Rinsing the black tank, is it necessary?

Some individuals try and keep their black tank as clean as their kitchen table. After dumping they rinse their black tank with a variety of gadgets.

I view my black tank differently. It is there to hold poop until such time as I dump it. I am not the least bit concerned about keeping it sterile. Not only do I not try to keep it sterile I do not care one whit whether it has a coating of slime on the sides.

Individuals who do rinse their black tanks say: "We don't treat our black tank like it's a septic tank. We treat it like it's a holding tank or remember, it is a HOLDING tank and not a SEPTIC tank. I would think that you would want it as clean as possible when not using it."

That is their opinion, I do not share it.

If I was going to haul milk or orange juice in my "holding tank" I would sanitize mine also. However, that is NOT what I am going to be putting in my "holding tank" so I do not see the need to sanitize it for the next load of .............you know what. Your views may vary.

The two sides obviously do things differently. Yet notice that neither have problems. This is obviously one of those instances where the proverbial cat can be skinned in more ways than one.

If you are one of the ones that wants to keep his black tank spotless here are some thoughts that might help you:

WATER SOFTENER According to some --- water softener is amazing and it works. Buy a couple of boxes of powdered water softener at the grocery store. You'll find it located with or near the laundry detergent products. Some prefer Calgon Water Softener because it dissolves quickly in water. Cheaper water softeners work just as well but dissolve more slowly. Dissolve two (2) cups of water softener in a gallon of hot water. Then, pour the solution down the drain into the empty tank. Use two cups of softener for each wastewater tank in your RV. The tank's drain valve should be closed otherwise the softened water will just drain out. Then use the tank(s) normally until it is full and drain it normally. Add a cup of laundry detergent to the black (commode) water tank at the same time. This will help clean the tank. The gray water tanks should already contain soap through normal use.

The water softener makes the solid waste let go from the sides of the tanks. If you've ever taken a shower in softened water you know that after rinsing the soap from your body your skin will feel slick. That's because all the soap rinses away with soft water. Softened water also prevents soap scum from sticking in the tub. Get the connection? With softened water gunk washes away instead of sticking. The same thing applies to your RV's wastewater tanks.

Now that I have included this information I am going to say again that we do not use any chemicals in our tanks. However, I suspect my tanks may have scum on the sides and bottom. But here again, I do not care what is on the side of my tank that is there to hold poop.

Proper dumping procedures and habits:


When you are camping and your RV is connected to a sewer/septic intake, leave the drain valves closed until the tank is full and ready to dump. Dumping a full tank provides a sufficient quantity of water to flush solids from the tank. Remember you need plenty of liquids to carry "flush" the solids out of your tank.

Notice that I said it was best to dump a full tank, however, that is not possible most of the time. We dump EVERY time before leaving a campground with a dump and that works for us because we use plenty of water and the one ply TOILET PAPER The stuff that comes out of my black tank isn't solids. It is a thin slurry if anything.


Leaving the drain valves open when you are connected to campground sewage allows the water to drain off without flushing out solid waste. That solid waste will collect in the tank(s) and cause problems (the "black pyramid") over time. More on the dreaded "Black Pyramid" later.


By dumping the black (commode) water tank first you are able to rinse out the slinky line with the water from your gray tank. This isn't rocket science but if you perform this sequence backwards you are going to have a mess on your hands. Think about it.


You may say I have never heard of "the dreaded Black Pyramid" - so am curious as to what it is!

The "pyramid" is what happens when solid waste goes down into the black holding tank and piles onto itself over and over and over. This can occur if you don't add a few gallons of water after you empty the tank, in order to prevent this. You don't want "stuff" hitting on a dry tank bottom where it can harden. It will also occur when you leave the valve open so that all the liquid drains off. This happens to RV'ers that set up for a few months. They think they can just open both their dump valves when they connect to the parks sewage system. They get away with it for a few weeks possibly months. But then it becomes one HORRIBLE problem when that "black pyramid" of solid stuff gets big enough to cause problems. Once it is that big it is a BIG problem. Those that have experienced one say it gets as hard as concrete. The only way to "repair" is to replace the tank, not cheap and certainly no fun. Repair shops do not want to perform this job, would you?

Other people explain the black pyramid like this:

Let your imagination work in overdrive........ If, by chance, you were connected to a sewer connection and were foolish enough to leave your black tank valve open. Each time you flushed the toilet the solids would fall down. Some of the solids would stay put while the liquids would drain off and down the slinky. Over time.................. how much time I have no idea, but over time the solids dry out and become hard. Those that have more knowledge than I say it gets as hard as cement. Anyway, that is what the dreaded pyramid of the black tank is.

Most people can see if they have a "black pyramid" forming by just shining a flashlight down their open toilet. When you look down you should see the bottom of your black tank. Of course you need to do this immediately after dumping, otherwise you are going to see stuff you probably rather not be looking at.

A few RVs are equipped with angled drain pipes below the toilet, unfortunately those will not be able to see the bottom of their black tank. Sorry!

A word about the tank level monitoring lights:

I do not depend on monitor lights. My black tank will hold 10-days of poop we know that because most years we dry camp for at least 3-months and are very aware of how long our fresh water will last as well as how long we can go on both waste water tanks. We NEVER go longer than 10-days without dumping. Most RV'ers tank monitoring systems do not work in any reliable fashion. Why worry about it? Just dump every few days. If you just have to know how full your black tank is look down the toilet hole with a flashlight.

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