Friday, February 10, 2017

Your RVs Black Tank Will Be Odor Free Starting Now

Odor Free, I Guarantee!

That's a big promise to make, but I am making this promise to you.  In all of our years RVing in different RV's, we have NEVER had a problem with black tank odor.  It's not luck, well, other than being lucky enough to figure our how to care for our black tank properly.  We have been in MANY RVs that have black tank odor, it's a common problem. And YES, we do run the vent fan while using the bathroom, that's what it's FOR! No odor.

I will ask that we accept the following assumptions:

  • Your tank is a standard RV design and install
  • There are no blockages, malfunctions or structural problems
  • You don't put anything into your toilet besides human waste and toilet paper

First of all, each of our RV's were purchased new. That's important to understand, and it matters because it makes the point that when acquiring a pre-owned RV, you will likely be inheriting someone else's lack of black tank psychology and care.  It's the most common problem that RVers have, whether you are in a small bumper-pull trailer, or a half-million dollar motor coach, they can all stink.  It's fixable, but let's understand the problem so you can tackle it.

If you have a new RV, you can skip to the section about Tank Maintenance.  If you keep just those few key points in mind, you will always have an odor-free bathroom, yes, odor-free.

Now, for those of you who either just bought a pre-owned RV with a stinky black tank (and maybe even grey tank!) or have had an RV for years and it has become stinky, take heart.  It is most likely that you can get it fixed easily and cheaply.  Rarely, the neglect is such that it is not repairable, as in a catastrophic blockage or something has broken.  Please be patient and take a moment to understand how the black tank works with you to get the job done, it is a TEAM effort, and you can do it.

It's Not A Septic System

First of all, let's get on the same page about what a black tank is and what it is not.  It is NOT a septic tank, and has almost no similarity in function to one. Your black tank is quite literally a simple plastic box with 3-7 openings cut into it (and size does not matter in this case!):

  1. A large round hole through which your toilets plumbing drops directly into.
  2. A large round hole through which your RV's plumbing attaches to exit the vehicle through a gate valve.
  3. A medium opening at the top through which a vent pipe attaches and exits through the roof. (This is important)
  4. (Optionally) A very small opening through which a very primitive, but useful sprayer head is attached to encourage solids that have attached to the side walls to release and fall to the bottom during emptying. This would be a black tank sprayer.
  5.  Likely 3 very small holes for your tank level probes, which make great hangers for toilet paper and hair which create false-full readings! (Note, NEVER flush hair down the toilet as in when cleaning your hair brush!)

Now, I have seen countless "remedies" for black tank management.  Putting ice into your tank to "scrub" it while under way (Doesn't work). Pouring various fool-proof concoctions down there to sanitize your tank (doesn't work).  The worst one: Pouring bleach into your tank: DO NOT EVER DO THIS!  Bleach is not only corrosive and will weaken or ruin your delicate rubber seals and valves, it will also KILL the natural bacteria which is critical to an odor-free tank!!  Bleach doesn't clean ANYTHING. It KILLS.  We don't want to kill anything, we want all the help we can get. Each little bacteria in there is your little soldier in the odor war!

My Sewage Smells Like Sewage!

All black tanks smell like sewage, that's what's in the tank.  That's not necessarily a bad thing.  The number one reason, believe it or not, that people have foul odor coming up from their tank is that it is so incredibly strong, that the roof vent cannot effectively dilute it or there is a vent blockage. Picture the smoke from a small fire, the smoke representing the odor, now picture the smoke from a huge fire with only a small opening to escape.  So, the very first thing you should rule out is that the small vent opening (it will have a round cap on it, usually) is completely free of obstruction.  Take the cap off, and shine a light down the vent tube and check for bees nests, debris, or anything else that might be blocking this vent.  The bulk of the tank odor will flow out of the roof vent as a gas, rather than build up in the tank, creating a stinky pressure bubble that presents through your toilet's opening when you flush.  It takes pressure to push that gas into your RV, the roof vent removes that pressure.  Make sure it's clear. If you smell a large amount of tank odor coming up from the vent, GOOD. That's what should be happening!

Passing Gas

Next, if the former owner (or you) have used your tank while hooked up to a sewer line, and left your valve open, you will have odor.  It will get worse over time as the solids from the toilet splat onto the bottom of your simple plastic tank and the liquids flow out of the tank.  Your tank will also be getting smaller and smaller. The solids will dry there into a concrete like mass (ever made paper mache'?) and eventually become very large, and quite permanent.  It will also reek like you would not believe and create gas so strong that the vent cannot hope to pass it all (smoke from a big fire).  This is extremely common. It is known by seasoned RVers as "pyramiding"  and "the mountain of death". One tell-tale clue that you have this going on is lack of tank capacity.  If you can only go a short time before filling your black tank, then it is likely due to this problem. If you have ever had dog poop pickup duty after several sunny days, then you know what happens to waste that is allowed to dry out. You could throw it and break your neighbor's window... but please don't do that. If you dropped it in a pail of water for a week, it would liquefy. Hold that thought.

Don't feel bad, most RV dealer sales people do not give good advice about tank management, and often have never even used an RV.  Always, always keep your black tank valve closed.  You want lots of liquid in there, making a nice big box of LIQUID waste that FLOWS out when you pull your valve.  Unless you are boondocking and conserving, always use plenty of water when you flush. Water is your friend.

Mountain of Death

Depending on how large your "mountain of death" is in your tank, it will take some time to remove it, but usually it can be remedied.  The most important thing is to keep it submerged in liquid to help it to decompose into liquid and eventually be gone.  This is the essence of black tank management: ALL solids eventually become liquid if they are soaked long enough.  Never allow them to dry out. A properly cared for black tank will always have liquid in it to some level.  Even while being stored.Your tank will thank you, your seals and valves with thank you, and your nose will thank you.  Water is also a natural odor-masking agent. If you cover reeking solids in water, the odor is greatly reduced, I bet you knew this already. This is the science of the P-trap under your sink! Try filling your black tank at least half full of water and notice if the odor is reduced.

Breaking It Down

Keeping your overly-solid solids under water is your number one priority.  It is impossible to soak human waste and toilet paper for long lengths of time and NOT have it become liquefied. It's that simple. And the liquid WILL flow out of the exit door! Your job is to make it liquid.  There are simply no short cuts to this unless you enlist the help of power sprayers and mechanical tools (which you can certainly do) but it is generally not necessary unless you are in a hurry.  One thing to be aware of when using mechanical means to dislodge solidified debris, is that large pieces can become lodged in your exit valve and block it, so be aware of this.  You may have the unsavory job of reaching back from the outside to dislodge it!  Make sure that you take advantage of every opportunity of being under-way to have sufficient water in your black tank to slosh around and work on dismantling your mountain!


We use three additives to supplement what happens naturally in the tank.  Without diverting too far into biology 101; the most efficient way that solid waste is broken down into liquid waste is by the appetites of anaerobic bacteria and beneficial enzymes.  These bacteria and enzymes are voracious consumers of waste, and the more you have, the quicker the waste becomes liquid.  You do not have to use additives, but we do as insurance that there is plenty in there.  It is interesting to note that human waste, from our own digestive tract (if we are reasonably healthy) comes pre-inoculated with this bacteria/enzyme cocktail. Isn't nature amazing? This gives us the ability to use any toilet paper we choose with a clear conscience.  Again, we consistently go 10-12 days between pulling the valve on our black tank. This tells us that there is nothing building up in there, or capacity would go down.

The first thing we add after every dump is simple septic bacteria/enzyme that you can buy at any Wal-mart. Rid-X, or the like. You can toss it into your grocery cart next time you shop. This assures that every square inch of surface in your simple plastic box is exposed to this amazing army of waste-devouring soldiers 24/7.

The other thing we add after every dump is a product from Valterra that we really like called "Pure Power Blue Waste Digester".  It is also a natural collection of the critters that work to get rid of the solids. It has the added benefit of a pleasant scent that keeps odors down. I saw a noticeable reduction in the amount of toilet paper that flowed out of the tank after we started using this (it became liquefied faster). That has to be a good thing. (We highly recommend having a clear plastic section or elbow fitting in your hose setup that allows you to see what is going on, very helpful and educational).

Once in a while (maybe every couple of months) I use Dawn dish soap. Why?  Well, more biology.  Human waste is loaded with FAT. That's right, plain old oils and grease.  If someone has gall bladder issues, there will be a lot MORE!  But that's for WebMD.  Anyway, I digress...  Over time, your sensor probes, and your tank surfaces will be coated with a layer of this grease.  Dawn dissolves grease efficiently without killing your community of bacteria and enzymes that you have so meticulously nurtured. I dump an entire small bottle down there after a tank pull every few weeks or so.  My level sensors always work, and I think this is a large reason why.

Tank Maintenance

This is how we care for the tank in a nutshell.  I am not saying this is the only right way to do it, but it has worked perfectly for us and we have many years experience of a LOT of RV use to reference. We will continue to do it this way. Plus, it's simple.

First of all, we keep the tank valve closed.  We only open it after the tank is really full.  A full tank is a happy tank. The longer you can go between dumpings, the longer you are soaking solids in the liquids and they are becoming liquid themselves.  The longer the enzymes and bacteria are left undisturbed to work their magic, the better.  Even when FULL, we do not smell our tank. If you dump your tank before it is full, you are wasting additives.  It's like getting new tires when you still have tread on the old ones.

When the tank is full (roughly 10 days of use for us and will vary depending on the size of your tank), we attach the tank sprayer hose (if you have one) and turn it on and then pull the valve.  We monitor the clear sleeve on our hose and note when the water starts running clear-ish.  The first thing you will notice when using a clear sleeve is that the solid waste does NOT empty in the first gush!  You will have several episodes of the solids building up at the tank opening, blocking the flow of the tank sprayer, and then WHOOSH! Another large amount of solids will flow by.  If someone simply pulled their tank and waited for the flow to diminish and thought it was empty, I can tell you that there is a LARGE amount of solid waste STILL in the tank! Do not do this.

If you do not have the benefit of a tank sprayer, you can simulate it very closely by dumping a couple of 5 gallon buckets of water down your toilet, or use your shower nozzle if it will reach.  It won't be spraying your sidewalls, but I don't feel that this is a big deal at all. The main thing is to flush out the solids that are hovering near the tank exit.

It is not important to try and get every bit of waste out of the tank. It's OK because whatever is left in there will be worked on in the next 10 days of soaking and become liquid.  There is always something left in the tank, but the important things is that your army of enzymes and bacteria are constantly at work making them liquid. Just get as much will come out in about 10 minutes of spraying.

When the water is mostly clear, we close the valve and after a few moments shut off the sprayer. This leaves a thin layer of water on the bottom of the tank and assures the rubber seal is submerged.  (Or pull the toilet open and let the water run for a bit). We then add our two additives as mentioned above into the toilet.  There are times when one of us dumps the black tank and then forgets to put the additives in. We still notice no odor.  We have not gone a long period of time without additives and I cannot say whether they make a huge difference or not. Perhaps we will try that some time!

That's it! I hope this helps you have a daisy-fresh bathroom, and I hope you will help others understand how very easy black tank maintenance is.  Far too many RVers suffer needlessly with stinky bathrooms!

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