How to handle your RV holding tanks and not total your camper or get covered in poop
I remember when we first started looking into RV life one of the things I was most concerned with was how to properly handle the RV holding tank. I had heard horror stories involving the black tanks and I could already see myself caught up in a scene like Robin Williams in the movie “RV.”
I distinctly remember searching out videos on YouTube about how to dump black and grey tanks. Well, I am happy to say that after 5 years of living in an RV I have learned a few things and I have spent very little time covered in poop…although that number is NOT zero, and I will share that story with you in the paragraphs to follow.
You need water in your black tank. Lots of water.
I am just going to jump right in here. It’s going to get gross. 🤢 But RV life isn’t always unicorns and rainbows. Sometimes it is stinky slinkies and sewer drains. When it comes to flushing toilets in an RV, the number ONE mistake people make is not using enough water. With the black RV holding tank, water is your friend. The more the better. The biggest problem with the black tank is when people don’t use enough water. The problem with that is that without enough water you end up with a “poop pyramid”. That is when the poop just keeps piling up below the toilet until finally it blocks the pipe. I can’t tell you how many times I have seen people post in the RV groups on social media that they have ended up with a poop pyramid and they want to know the solution to fix it. The solution is not pleasant. It isn’t pleasant at all. You’ll need a big stick. Yep. That’s right, you have to push the poop pyramid down. Smash that crap, pun intended. Once you have the poop pyramid broken up, you can flush lots of water down the toilet and that will help break up the solid materials. To keep a pyramid from ever building in the first place you need to be using LOTS of water when you flush. When we flush our toilet, we always let the bowl fill up with water a second time and flush again. Sometimes I will even do that a third time. The more water in your tank the more it will help break up any solid material in the tank and help to keep a pyramid from ever forming in the first place.
Do you have to use RV toilet paper?
For YEARS, we were buying special RV toilet paper. The absolute last thing I wanted was for solids to build up in our black tank and leave us unable to dump our RV holding tanks. Special RV toilet paper ain’t cheap. Finally, after a few years, my friend recommended that we just get regular septic safe toilet paper. I didn’t want to just take his word for it, so I purchased a pack of the septic safe TP we wanted to use and also a pack of the RV toilet paper we had been buying. I took some of each and placed them each in a jar of water and let them sit. After about half an hour, I slightly shook them and saw that each had dissolved the same. The ONLY difference I saw was the the RV toilet paper had all settled at the bottom of the jar and the regular septic safe TP had dissolved and remained suspended in the water. If you have a special septic safe toilet paper you’d like to use, I highly recommend this method to test and see if it will work for you! After our test, we have been buying the brand of septic safe TP that we want and have been saving lots of money on TP!
Should you leave your gray tank valve open?
This is a. VERY common question, and if you ask in the groups you will get answers from each side. But here, I will discuss the proper way to use your gray tank. First of all NOTHING but soap and water should ever be going down your sink drain. Never put grease or anything like that down your drain. That’s a great way to really mess up your gray tank. With that out of the way, let’s discuss whether or not you should leave the vale for your gray RV holding tank open or not. If you are on full hook ups, you should leave your valve OPEN. Here is why. I have worked in a campground. I can not tell you how many times I have seen someone close their gray valve and then they, or their kid, end up leaving a sink running at night which ends up flooding their camper. That is a perfect way to ruin a brand new camper. I remember I once saw this happen to a camper that a guy had literally just bought brand new and parked immediately at the RV park. He hooked up water and power and didn’t hook up his sewer hose. He used the sink and somehow forgot to turn it off before leaving for the afternoon. Needless to say his kitchen sink overflowed and flooded his brand new camper. I know a lot of people will say that there is a risk of an RV park’s sewer line backflowing into your gray tank if you leave the valve open…and yes…that is a risk. BUT, there is a much higher likelihood that you will accidentally flood your own camper by CLOSING the gray RV holding tank valve while hooked up to city water. Another argument that people will give you for keeping the gray valve closed while on full hookups is that they say you will have “sewer smell” in your camper if you keep the gray valve open. This should NEVER be the case as you have P traps under your showers and your sinks. P traps are the curved drain pipes that fill with water and block any sewer smell that would come up. If you smell sewer, then something is wrong with your P trap.
How to dump RV black tanks and gray tanks
Now, you will remember from above that we keep our gray line open when on full hook ups. When I see that it is time to dump our black tanks, I will go close the gray valves and take a shower, do dishes, or do a load of laundry to let the gray tanks fill up about halfway. OK, here is where we are getting to the nitty gritty and where I share my first story about getting covered in poop. I am going to assume your black tank is full. Never dump your tank unless it is full. It needs to sit there and marinate for a while to break up any solids. First and foremost, make SURE your sewer hoses are all hooked up to your camper and that you are properly connected to the RV park sewer. Most parks will have a threaded sewer pipe and you can thread the sewer hose elbow into it to make sure it is secure. Some parks do not have threaded sewer pipes and in those cases, I like to put something heavy on that sewer elbow to make sure that sucker stays DOWN. Speaking of sewer elbows, as gross as it sounds, you definitely want a CLEAR elbow so you can make sure that everything has cleared out of the hose. We use THIS ONE. 
Now that you have the correct sewer elbow, and you have made sure your sewer hoses are actually connected to your camper and secured to the RV park sewer line, it’s time to actually dump your tank. The following is where I goofed once and ended up covered in poop. START SLOW. When you go to pull your black tank valve start slow. VERY SLOW. This will help to make sure there are no leaks or cracks in the hose or any loose connections. I once walked over to our rear black tank and yanked that valve wide open like I was playing a pinball machine. The problem was I was unaware of the major crack in the sewer hose up near the connection. It immediately started spewing sewer water everywhere and I was left with no choice but to reach my arm back in and close the valve. My arm was met by a Niagara Falls of poop. But at least nobody saw it…or so I thought. It was at this very moment that several of the teens behind me in the RV park said “did you just get covered in poop”??!! I would have facepalmed, but my arm was covered in absolute nastiness. From that point on, I have always remembered to START SLOW and then open the valve more and more until fully open.
After dumping your black RV holding tank, you will want to close the valve. NEVER EVER leave your black tank valve open. Remember? Water. is your friend. If you leave the valve open, you will end up with the whole poop pyramid thing. After your black tank is empty, and the valve is closed, you will want to open the gray tank valve. This will allow the gray water to somewhat flush out your sewer hoses.
Time to flush your black RV holding tank
Every once in a while you will want to do a black tank flush. This is also how many campers end up getting totaled and how I almost totaled OUR camper, and how my friend made fun of me for it….and then he did the exact same thing. On your camper, you will find a black tank flush hookup. I think this goes without saying but you do not want to use your drinking water hose for flushing your black tank. Have a separate hose for this. We use a black hose just to make sure there is never any mix up. After you’ve dumped your black tank, leave the valve open and hook up the black tank flush hose. Turn the water on at the spigot and make absolutely sure you see the water coming out at the clear elbow. (This is where a clear elbow is very beneficial). Now, I know what you’re thinking, “shouldn’t I close the black tank valve and let the black RV holding tank fill up so it really flushes out the whole tank”? The answer is, well…it is dangerous. But you CAN…if you’re careful. If you have the valve closed and you over fill the black tank, it will overflow INTO your camper with poop water and/or overflow up the black tank vent pipe and up onto the roof or inside the ceiling itself.
Let me tell you a story. We were at a Thousand Trails park in Virginia right after we started fulltime RV travel life. Angela was away with the kids and I decided to stay back and do some things on the camper. One of those things was to dump the tanks and do a flush on the black tank. I went outside and hooked up the flush line, and turned the water on. BUT, I had not yet pulled the valve open. I went over to pull the valve and busted my head wide open on the slideout. I was bleeding like I was getting paid by the gallon so I ran into the bathroom to doctor myself up. While in there I started smelling sewer…BAD. It was at this moment that I remembered I had never pulled the valve, so I ran outside like Usain Bolt and yanked that sucker wide open. The water came out with such force that it actually busted my sewer hose open in several places. (This is actually the first time I was ever sprayed with sewer water) I knew then that it had probably started going up my vent pipe and I had caught it just in time before it made it to the top of the vent pipe. AND the flush valve inside the toilet had been sealed tight enough to keep the water from coming up into the toilet and overflowing inside the camper. So it had apparently built up lots of pressure and that is what caused the hose to bust open when I dumped the tank. It was a VERY VERY close call. Here is a photo of our first RV at that very park…maybe on that very day. 
I told my friend Brian this story and his exact words were “rookie mistake”. Well, it wasn’t long after that, that HE was doing a black tank flush and he closed his valve. A few minutes into it, he went into the house and his wife asked if he wanted to join the family for a grocery shopping trip. He totally forgot that he was flushing the tank. The whole family loaded up in the car and they started off. At the last minute, the oldest son changed his mind and decided to stay back. He went into the bathroom and saw water coming up the toilet and immediately realized what was happening. He ran out and pulled the valve. Had he not stayed behind, their camper would have been totaled. No doubt.
So here is my advice with doing black tank flushes. You can close your valve. But as SOON as the valve is closed, set an alarm to remind you to open it a few minutes later! I have found that it typically takes about 8 minutes to fill our tank. So when I close my valve, I have siri set an alarm for 7 minutes. During the fill process, I actually go flush the toilet a few times and look at the water level below the toilet just to be sure. I have my alarm set EVERY time now.
The last thing I will say about black tank flushes is to NEVER leave your flush hose hooked up. I have seen several people who have a Y hooked up to their spigot and they leave the sewer flush hose on there and hooked up to their camper. The problem with that is anyone can come by and turn on the spigot and end up inadvertently flooding and totaling your camper. It happened once at an RV park I know well. Someone turned on a man’s water spigot while his black tank flush hose was attached. He was gone to work for the day. When he came home, he arrived to his camper overflowing with poop water from inside.
RV Black Tank Treatments
A great way to make sure that your black tank just start stinking so bad you have to move out of your camper is to use a regular black tank treatment. Something like these Camco Drop Ins should work great for regular treatments. One thing you will notice almost immediately is that the sensors on an RV black tank NEVER read correctly. They almost always show full. This is because TP, Poop, etc get stuck on the sensors in the tank. I usually don’t worry too much about it, but I DID recently find a black tank treatment that actually worked well enough to make my sensors show EMPTY for the first time in about 2 years. We got the Walex Commando drop ins and they worked perfectly.
RV Tank dumping step by step
- Make sure the black tank is actually full. Your sensors could be wrong.
- Go close your gray tank valve
- Take a shower, wash dishes, etc to fill your gray tank.
- Go pull your black tank valve. (Remember to start slowly) SIDE NOTE: You can do a flush afterwards if you want)
- Close your black tank valve when you’re done dumping/flushing the tank.
- Open your gray valve
- Leave your gray open if you’re on full hookups