Black Tank Basics

I’m seeing a lot of posts, questions, and issues surrounding the black tank, so let’s break down how it works, what to do with it, and why it matters.

First, what is the black tank?
The black tank is one of two different waste tank systems commonly found in an RV, and is specifically for waste from the toilet.

Second, what is happening in there?
Your black tank is much like a septic tank you might have at home, and is mostly a place to start breaking down waste before disposing of it. By the way, please be sure to always dispose of your black tank waste in a proper place, not just on the ground or in the open.

Third, why is it different than the gray tank?
The gray tank is for ‘used water’, that is, water and other liquids drained down the sinks that doesn’t have waste in it. While you won’t drink gray water, and you probably don’t want to use it for washing dishes, it CAN be used for watering plants, creating weighted jugs, and other non-potable uses.

Ok, let’s get down to business. Best practice for using your black tank is:
1) Keep the valve closed until it’s time to dump the tank.
2) From empty, put a gallon or two of water in there.
3) Put your choice of black tank treatment in there.
4) While using the toilet, be sure to use plenty of water; I like to use twice as much water as anything that goes into the toilet, which includes liquid waste, solid waste, and toilet paper.
5) Once the tank gets 3/4 full, it’s time to think about dumping. Once you’re hooked up to a sewer or dump station, go ahead and fill the tank from the toilet (just hold the pedal down and let the water flow in).
6) Dump the tank, and take note of how well things flow out (this is why clear elbows or connectors are important).
7) Be sure to rinse the tank out and dump it again until you have clear water coming through your sewer hose. You can run a hose into the water closet and down the tube, or just use your built-in tank rinse connection is you have one.
8) If you empty your tank before you drive somewhere, drop a cup or two of cleaner in there, like ka-boom or purple power, and add a few gallons of water so it’ll slosh around and clean the inside of the tank. You can also add a bag or two of ice to add some scrubbing power.

I’ve seen and heard of a lot of issues with the sewer lines and dumping the tanks, so let’s go over some things NOT to do.
1) Don’t leave your black tank valve open unless you’re actively dumping your tank.
When you leave the valve open, the waste you flush goes straight to the valve with no time to be broken down. This always causes a stoppage, which just creates all kinds of problems. Leave the valve closed until it’s time to dump.
2) Not using any kind of treatment.
When you don’t use any kind of black tank treatment, you don’t have anything in your tank to help the process of breaking down the waste. Without treatment, waste breakdown take 4-10 times longer than with treatment, which means you’re probably going to have issues with clogs if you don’t use treatment. Always use a tank treatment.
3) Don’t flush excess paper.
Really, don’t flush excess anything. The only stuff that should be going into the toilet is urine, feces, and toilet paper with feces on it. Putting TP with urine on it in the tank is optional, but the more paper you put in there, the more water you need, the faster it fills up, and the more you’ll have to do to keep it running smoothly.
I recommend your urine paper go into a wastebasket (with a lid on it!), and your feces paper go into the toilet.
Also, ladies, your sanitary products are best put into a wastebasket with a lid, not into the black tank.

Last but not least, what to do if….
If your toilet is clogged at the top (in the bowl) don’t reach for a plunger, it won’t do any good. In fact, you don’t even need to carry a plunger in your RV, it won’t work. Instead, you need a stick, 2-3″ across and 2-4′ long. Turn the water off to the RV, open the valve all the way, and use the stick to push the stuff down. The bottom of the toilet is connected to the top of the tank, and there is no ‘s-bend’ or trap like your toilet at home, so just give the stuff a little help down the tube.
If you’re having trouble getting your tank to drain into the sewer, fill it up with water and tank treatment, let it sit an hour or so, then drain it again. Repeat as many times as needed.
If you can smell your black tank, you need more, or better, treatment. For quick relief, drop some dish soap in there and fill the tank with water, walk around to shake up the RV a little bit, then dump it. For long-term relief, use a better treatment, or just more if it, and make sure to use 2:1 water:waste.

So there you have it, my thoughts and experience in dealing with your black tank. If you take care of your tanks, they’ll take care of you, and remember, it only smells bad when it’s treated badly!

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