Don’t Leave Your RV’s Black Tank Valve Open

#2 Lesson in the “Do As We Say, Not As We Do” Series

There is a reason why this is number two in our “how to”, or rather, “how not to” series. It pertains to your RV toilet and holding tank – or black tank – and how to keep it from getting clogged or letting things “pile up”, so to speak. Here’s what we have learned about RV holding tank maintenance.

What are black and gray tanks and should I be afraid of them?
I have to admit when I learned about RV holding tanks and that I would have to hook up and empty them out, I wasn’t a happy camper. Many miles and camping trips later, I realize that it’s really not a big deal, as long as they are maintained and operated properly. We have learned a lot about RV holding tank maintenance.

RVs can have three types of holding tanks:

1. Fresh water tank for storing water you will use when you’re camping without water hook ups, such as off grid camping / boon docking. The fresh water tank is connected to your RV plumbing system to provide water to the sinks, shower, and toilet. You should also have a fresh water level monitor in your RV so you know when the water level is running low.

2. Gray water tank that holds waste water from your RV sinks and shower. There may be more than one gray water holding tank. Our RV has one for the kitchen and one for the shower/bathroom sink. You can monitor the level of wastewater in the tank by viewing the monitor panel in your RV. Installed sensors detect the amount of water in the tank at for example 1/4, 1/2, 3/4 and full tank levels. A gate valve is located on the side of your RV allows dumping when the tank is full.

3. Black water tank that holds the waste that you flush down your RV toilet. You can also monitor levels of waste in the black tank via your RV monitor panel. A gate valve on the side of your RV allows dumping when the tank is full.

Black and gray tank usage and operation (without campground sewer hookup)

Using and Maintaining RV Holding Tanks

Keep valves closed until tank contents are ready to be dumped.

When the tanks are about 3/4 full, as indicated by the sensors on your RV monitor panel, it is time to dump out the contents! Note that the sensors are not always entirely accurate, and smaller RVs may not have sensors. Gunk like bits of toilet paper can get stuck to sensors and cause an inaccurate reading. In those cases, you will have to gauge how quickly the tanks will fill up. This will vary based on how often you are using them and how many people are using them. It is better to empty the tanks when they are at least 3/4 full, as the force of the water creates a stronger flow to help ensure that solids are flushed out.

Connect a high quality sewer drain hose, ensuring that all connections are secure. One end connects to your RV’s black tank valve, and the other to the dump station’s sewer valve.

Open the black tank valve and allow contents to drain completely. It is important to drain the black tank first. Draining the gray tank afterwards will help to clean out the hose and connections.

Flush the black tank with clean water. Leaving the black tank valve open, connect a water hose to your RV’s black tank flush inlet. It should be labeled and located near the black tank drain valve. Turn the water on and allow to run until the water draining from the black tank runs clear. We use a clear connection elbow so we can view the water while it is draining. If your RV does not have a built-in flush system, you can get a flush adapter, such as the Flush King reverse flush valve.

Open the gray tank valve and allow contents to drain completely. It is not necessary to flush the gray tank every time, but should be done occasionally to keep it clean and to help keep any residue and particles from building up on the tank sensors. Close the black and gray tank valves after finished draining. You will want to fill the black tank again to about 10% of capacity before traveling again. Some folks recommend filling it up more than that before traveling in order to let the water slosh around and continue to clean the tank out. We haven’t done this, but it can’t hurt.

What if the campground has sewer hookups?

I can’t say it enough times, DO NOT LEAVE YOUR RV BLACK TANK VALVE OPEN! It is okay to leave the gray tank valve open, allowing wastewater from your gray tank to drain directly into the sewer. We have two gray water tanks, one for the shower and bathroom sink, and one just for the kitchen sink. We leave the valve for the shower / bathroom sink open, but leave the kitchen sink valve closed until it is nearly full before opening and emptying it out. This helps clear out small food particles and grease/oil. It is important to leave the gray valve open if you have a washing machine or dishwasher in your RV so you don’t overflow the holding tank.

Some make the mistake of thinking that when the black tank outlet is connected directly to sewer at a campground, the black tank valve can be left open, allowing the waste from the black tank to continuously empty out into the sewer. This is a bad idea, since all of the liquids will drain out and solids will be left in the tank. Solids will dry out and pile up, causing clogs that can be very difficult to clear out. Leave the black tank valve closed until about 3/4 full, then open the valve and let the contents drain into the sewer. After closing the valve again, be sure to fill the black tank to about 10% capacity with clean water.



What to do if your RV’s black tank gets clogged

When we first started RVing, I have to admit that we did leave the black tank valve open and we did, indeed, have a clog. I have read quite a few tips and tricks about fixing a clog in your RV toilet / tank. This included putting hot water into the toilet, pouring ice cubes into the toilet and driving around to break up the solid waste, using a cleaning wand, enzymes, etc. Though we used a combination of things, we found some valuable information at the Kleen Tank website. Kleen Tank advises RVers to use enough water to keep clogs from happening in the first place, without using any chemicals – and also offers a tank and/or sensor cleaning service if issues occur. They also recommend using a mixture of pine oil cleaner and Calgon bath beads for a tank deodorizer rather than using chemicals. See Kleen Tank for details. We have not used their services so cannot recommend them, but we have used their recommended tank deodorizer.

To see more of our “Do as We Say, Not as We Do” series, and other articles, go to the New Life RV Blog page.

Let us know what products work best for you for RV tank maintenance!