If you have a newer RV you can optionally employ the tank wash system if you have one installed on your black tank. This system uses a series of jets inside the tank to help blast away any buildup on the sides and bottom of the tank. This also helps to ensure your tank sensors work correctly.
To use the system you will need to attach a water hose to the inlet, turn the water on and let the tank rinse for a few minutes. You should use a standard garden hose for this and not your RV water hose in case there is a backflow of the water. While rare, there is a chance that water could flow backwards from the tank back into the water hose.
There are 2 methods you could try to see which works best for you:
- Leave the tank valve closed and let it fill up, then drain it, or
- Leave the valve open and let the water run through the tank and out the hose.
Personally, I find filling the tank completely once or twice works best for us, but some people prefer to just let the rinse happen while the valve is open. If you’ve never done the completely fill method before it’s probably best just to leave the valve open and let the water run out. The nozzles inside do a pretty good job on their own.
One thing to keep in mind is if you do leave the valve closed you need to know what your capacity is. This may involve simply looking down the toilet as the tank fills, or timing it.
For example, I know when I hook up the hose using our city water pressure it takes 4 minutes to completely fill our black tank. So when I rinse it, I start the stopwatch on my phone then turn on the valve to let water run into the black tank. At the 4 minute mark I turn off the water and open the tank value. If I do this 2 or 3 times my tank becomes completely clean.
If you don’t have a rinse system on your tank, there are aftermarket systems you can buy and install, or a simpler method is to use this reverse flush valve. To use it you’d put it between the hose and outlets on your drain. Once the tanks are drained, attach a garden hose and re-open your black tank and turn the water on. Water is forced back up into the tank, helping to loosen anything that could be stuck to the bottom and sides of the black tank. It can also be used to help clean your grey tank. This is particularly useful if the tank sensors of your grey tank also register as being full after they were emptied.
Another tool you can use is a wand like this that attaches to a garden hose. Once the tank has been emptied, open your toilet, put the wand down and open the valve. The powerful spray head words similar to built in tank rinsers, helping to loosen and remove stuck on particles.
We’ve used both methods and they both worked relatively well. One thing I should mention with regards to the wand is you want to be sure to control the water pressure. The last time I used it the water pressure coming out of the hose was so great that it blew the end off of the tool :(
For more information on maintaining the sensors in your RV holding tanks, please read this article.