How to Maintain and Operate Your Black Water System
By Warren Petkovsek
Well, it was bound to come up sooner or later. That’s right; the dreaded and much maligned RV black water system (GASP!). This rather unpleasant tank and its contents have long been the subject of contention and even humor in movies such as National Lampoon’s Christmas Vacation and RV with Robin Williams. The rule in my family is, “If it’s hot, dangerous or dirty then its Dad’s job.” The RV black water system definitely falls into this category because hot weather is a certainty in my part of Texas; black water systems could possibly be dangerous to your health if proper precautions are not taken and finally the “dirty” part is somewhat obvious. Well, it doesn’t have to be all that bad. Just like my job in the refinery, as long as harmful or dangerous substances stay contained in their proper tank, receptacle or pipeline then everything is OK. Let’s discuss how we can keep everything contained and working properly.
To start out, the black water system is somewhat explained to a new owner by the salesman, technician or, in the case of a used rig, the previous owner. This system is often not adequately explained to the new owner, but even if it is there are many things that are easily forgotten in the avalanche of information that bombards the novice RVer. To make matters worse, a well meaning and otherwise helpful fellow RVer will often give bad information when discussing the black water system. The fact is that this dreaded system isn’t really all that hard to maintain and the contents can be easily and safely managed by following a few simple rules and precautions. Please trust me on all of this; I’ve never had a problem of any kind in all my many years of RVing by following these rules, but I’ve seen many folks with their fair share of problems and mishaps and I’ve learned from their mistakes so please read this carefully and take these suggestions to heart. Here we go.
The first thing you will need for your black water system is a good quality sewer hose. What’s that you say? Your RV came with a sewer hose? Well, let me tell you that there is a very good reason why that hose was included with your RV. They couldn’t find anything cheaper. The sewer hose that came with my new fifth wheel was that way so I got a good quality hose and kept the original hose in case I found myself in a situation where it was a long way from the sewer connection on the trailer to the sewer in the campsite and I had to use two sewer hoses joined with a connector. ‘Bad idea. I could have used rolled up newspaper and been better off instead of using that cheap hose that came with the rig (‘Just kidding. Don’t really try this). That cheap hose sprouted many leaks the first time it saw liquid and it had never been used before! ‘Time to make a Wal Mart run! You can buy RV sewer hoses at department stores, RV dealers or at Camping World and you will probably find them in three different grades and price ranges. Why fool around with the cheapest sewer hose that you can find or, for that matter, even the mid grade? Even if the best quality hose you can find costs twice as much the quality is worth it if it will prevent your black water system from losing containment. As I mentioned before, you will sooner or later find yourself in a situation where your sewer hose just isn’t long enough. Be sure to carry a second hose and a coupler to join them together. You will also need to have the plastic fitting or the rubber “donut” device that joins your hose to the sewer hookup in the campsite. These items probably didn’t come with your new RV so add them to your shopping list.
Many RVs have a metal rear bumper that doubles as a place to carry your sewer hose. This bumper will have a rubber cap on one or both ends. You can carry your sewer hose there and it will be out of your compartments and separated from everything else. I have done this with my first trailer for a long time and then one day I discovered some pin hole leaks in my sewer hose caused by friction between the steel bumper and the sewer hose. This is why many RV manufacturers are getting away from this bumper storage idea. I solved the problem on my old rig by getting a PVC sewer pipe that was nearly as long as the width of my trailer. I also mounted a screw-on cap on each end of the pipe and I mounted it under the trailer from side to side attached to the frame with metal strapping and heavy duty zip ties. This set up easily carried all of my sewer hoses and they were accessible from either side of the trailer. I also drilled several small holes in the pipe to help the residual moisture evaporate between trips and reduce mildew. I have done something similar with my new fifth wheel except I didn’t mount the PVC pipe to the frame. I simply store the pipe in the basement storage compartment because I have plenty of room for it. I also didn’t drill any vent holes in this pipe because, obviously, I didn’t want any nasty water in my storage compartment. When I get home I will take the pipe out and remove the end caps and let things dry out for a day or so.
I am amazed at the health risks that people will take when handling their sewer hose and black water connections. Most folks will handle the sewer hose bare-handed and probably will not wash up afterwards. I have used disposable latex gloves for this job for years. These are the kind of gloves that are used by paramedics, doctors and nurses. You see them used on TV all the time by crime scene investigators. These gloves are inexpensive and disposable. I keep a box of them in my basement storage compartment near the Rubbermaid box that contains my sewer connections. They also come in handy for messy jobs around the house and shop. I always wear them when changing my oil or handling the messy grease gun.
Have you ever seen someone breaking camp and they rinse out their sewer hose at the campsite water hydrant? That’s right; they will do this and the next person to use that site has to hook up their drinking water hose right there where someone else’s nasty sewer hose and filthy hands have been. I safeguard our health by sanitizing the fresh water connection before hooking up the fresh water hose. I do this by spraying the campsite hose connection and valve handle with a 20% bleach solution from a plastic pump spray bottle that I carry in another Rubbermaid box with my water hoses and plumbing connections (Can you tell that I’ve organized my stuff with Rubbermaid containers?). Also, never ever use your fresh water hose for anything but fresh water. I actually see people rinsing their sewer hose with their white drinking water hose. ‘Talk about a bacteria festival! I carry a green garden hose for that purpose and for other jobs that require a water hose and I never use that for water that is to be consumed by people. I further protect my white fresh water hoses by draining them and hooking the ends together when I am storing them after use. This keeps them clean and keeps any foreign matter from entering the hoses.
A very common mistake that many RVers make when camping in a site with full hookups is leaving the black water dump valve in the open position. They think that by doing this that they don’t have to worry about the black tank filling up, but they are creating a much bigger problem. By doing this they are making two serious mistakes. They are draining the chemicals that they previously added that are needed to help eliminate odors and they are also allowing solids to build up and harden on the bottom of the tank. The black water tank drain valve should remain in the closed position and the level in the tank should be allowed to fill with use. Black water tanks typically hold 40 gallons or so and they can go an amazingly long time before they need to be dumped. My wife and I once stayed at a Texas state park without sewer connections at the campsites. You had to empty the tanks at a dump station when leaving the park. We were also joined by my mother-in-law for about half of the time we were there. We stayed for 16 days and between the three of us we never did fill up the black tank. This is because an ordinary flush of an RV toilet will not use nearly as much water as your residential toilet at home.
This is how to operate and maintain your black water system. Do this exactly as I describe and I promise that you will remain trouble free.
Never dump the black tank until it is at least 2/3 full. Flush water into it if needed. This will help to carry out the solids.
The night before dumping the black tank close the dump valve on the grey water tank to allow that level to build some. The grey tank is later dumped after the black tank to rinse out the sewer hose.
After dumping, rinse the black tank with fresh water by using either a water hose down the toilet or by simply using the flush valve for 2 – 3 minutes. Do this with the dump valve closed allowing the level to build slightly. Dump the water and repeat at least three times. Some newer RVs have a “San-T-Flush” system where a water hose can be hooked up to the trailer and a high pressure water spray cleans the inside of the black tank. This can be added to any RV by your dealer’s service department or you can do it yourself if you are handy with tools.
When you are finished rinsing out the black tank close the dump valve, add several gallons of water and then turn the water supply off so that you can add the toilet chemicals. Use any commercially available RV toilet chemicals and you will be fine. After adding chemicals add a little squirt of Dawn Dishwashing Liquid. I learned this trick from a couple of full-timers and there is never any odor.
Be sure to use a dedicated green or yellow water hose for rinsing out the sewer hose before you store it. If you have an old white drinking water hose that you want to use for this purpose be sure to mark it with duct tape or something so that you will know that it is no longer used for fresh water.
If you follow these simple procedures you should never have any problems with your black water system, but what if you do? You may have bought a used RV and you are not sure that he previous owner was this careful or maybe you became a little lax in following my guidelines (Shame on you!). If your black tank becomes plugged up with solids and it won’t drain try this tip. I heard about it when discussing this problem with some other veteran RVers. I’ve never had this problem myself, but I have suggested this tip to someone else with a plugged drain when we were park hosting and it worked. Close the black tank dump valve and disconnect the sewer hose from the park sewer (leave it connected to your RV). Hold the loose end of the sewer hose as high as you can above your head, get someone else to fully reopen the black tank dump valve and slowly add water from a water hose. When the sewer hose is full or nearly full quickly (and carefully) lower the sewer hose and stick it back into the park sewer connection or dump station sewer. This causes a siphoning action that will very likely loosen the solids and carry them away down the sewer. The fellow that I suggested this to said that it worked on the second try and took care of his plugging problem. If you suspect that you may have some solids still in your black tank you can simply add water to the tank until it is about 1/3 full and add several squirts of dishwashing liquid. After that add four or five bags of ice and do this right before you hit the road. As you drive the detergent will help clean the tank and the ice is a great scrubbing agent. When you get home or to your destination the ice will be melted and the water can then be dumped down the sewer as normal. Then simply add water and chemicals as usual.
There is also a product called “Pure Power” that is made by O.P.Products, Inc. It is mixed at the rate of 2 ounces for 40 gallons of water, but it can be mixed stronger. This will liquefy the solids in a black tank overnight. This product is available Where RV related products are sold and the company can be contacted at 1-800-411-8801 or on line at
Well, that’s about it on black water systems. I hope that you never have any problems with this, but if you do just give me a call. I will give you moral support and a shoulder to cry on, but just don’t expect me to come and clean up your mess.
Good luck and happy trails!
Warren Petkovsek has been an avid RVer for over several decades. He lives in Lumberton, Texas with his wife, Myra. A former teacher, band director and professional musician, Warren is now retired from the petrochemical industry. In addition to being a freelance writer he is also a school volunteer, a Texas State Park volunteer and has been a Boy Scout Leader for many years. Warren would be delighted to answer any RV related questions that you may have and would be happy to send you some or all of his other articles. He can be contacted at firstname.lastname@example.org .