As a mobile RV tech I have addressed many black tank problems, ranging from simple clogs to tanks that have fallen off their supports. An RV black tank has a very important job to do and works well when it is given the proper tools and conditions.
The black tank is not complex, and works by breaking down the solid waste into a slurry, allowing it to exit the tank without clogging. The solids are broken down by bacteria and lots of water. Some of those bacteria give off methane, others do not, and methane is one of the chemicals that gives black tanks their unpleasant smell. The key is to encourage the less-stinky bacteria to flourish and keep the stinky buggers away. Given a good environment and enough water, the solids are broken down within 24-48 hours.
Here are some questions I’m frequently asked about black tanks:
I have a clog, will a plunger work?
A plunger is not the best tool for RV toilet clogs. More often then not, the plunger will just make things worse by causing leaks in the system. The best tool to clear an RV toilet clog is a hose that can push through the clog and spray water in all directions to break up the clog as the hose is pulled back. Most RV techs like me make their own from a section of PEX hose, but this Valterra tank flush wand could also be effective.
What chemicals should we use in our black tank?
Most black tank chemicals out there are nothing more than heavy perfumes and water softeners. The material I use, and encourage my clients to use, is Happy Campers Organic RV Holding Tank Treatment. This product provides an excellent environment for the good bacteria to thrive and discourage the bad bacteria. When we first switched to this stuff, the difference was quick and significant.
Incidentally, if you ever notice an unpleasant smell coming from your gray tanks (galley/kitchen tanks are famous for this), you can add Happy Campers to your gray tank, too.
What do I do with the gate valves?
Never ever leave the black tank valve open! That would allow the fluids to flow out and the solids to build up and harden, causing the dreaded “poop pyramid.” Believe me, you do not want to be in that situation. Use the tank, and dump it when it is at least 2/3 full. The bacteria cannot do their job without water. When it’s time to empty the tanks, open the black tank valve first. When that tank is empty, close the gate valve and open the grey water tank valve. You do not want to open both gate valves at the same time. This could allow the soaps and chemicals from the grey water to contaminate the black water environment and kill off the good bacteria that remain, as well as discouraging the growth of new bacteria causing a stinky black tank again. Don’t forget to close your gray tank valve when you’re done, too.
Note for those who have onboard laundry machines: there should be a separate drain or valve for that system. That drain valve should be open anytime you are using the washing machine. If your washer drains into your grey water tank, then leave your grey water valve open when you are using the washing machine.
How often should I flush the tank using the tank flush sprayer?
The simple answer is to flush it when you are done with it for a while. If you’re full-time or will be traveling awhile, there should not be a need to flush the tank between dumps if the tank’s bacteria are healthy. Flushing out the tank with the tank sprayer will clear out all of the bacteria in the tank you will have to start a new colony from scratch.
Hope this helps. Happy Camping!