Grey and Black Tanks 101

I didn’t know a thing about grey and black tanks when I bought my first RV. I bought it from an individual and he didn’t provide any instructions on the process. I was nervous thinking about my first dump station stop because I didn’t want to hold up the line, look stupid or make any messy, embarrassing mistakes so I started researching. I learned the basics that way but I found there is a lot of good and bad information out there. I learned much more by gaining an understanding how they actually work.

Now that I have substantial experience I’ll share some of my own tips.

What are the grey and black tanks anyway?

Are the tanks really grey and black? Not necessarily. It refers to what’s in them rather than the color of them. The sinks and tubs/showers drain into the grey tank. Toilets drain into the black tank. At the sewer connection you should see two pipes coming into the one large one that you connect the sewer hose to. The larger of the two should be from the black tank and the smaller is from the grey tank.

They should each have a blade valve with a handle to open and close them. The valves are often at the sewer outlet but some RVs have “remote” valves. Some RVs may also have multiple grey and/or black tanks. They may all go to one sewer connection or there may be more than one. The method to open and close the tank valves can vary with different RVs but the concept is pretty much the same across the board.

Recommended items

This is what I carry in my camper: 

  • A Rubbermaid “Sewer Tote”. It’s a great way to keep everything organized, easy to grab and put away and keep from contaminating other things in the storage compartment.
  • Two RhinoFLEX Sewer Hoses. One is usually enough but may not always be long enough to reach at some campsites. Also, you never know when one will get stepped on, driven over, punctured or just worn out. Plus, I’d rather not pay the high price to buy one at a campground if I’d unexpectedly need one fast.

  • Valterra Flush King Reverse Flush Valve. This.Is.Awesome. Full review coming soon!

  • 25ft Water Hose (dedicated for the Flush Valve). Mine is just a regular drinking water hose that I retired to sewer duty. I wrapped black electrical tape around it in a few spots at each end so it doesn’t accidentally get used for drinking water again.

  • Wye Connector with Shut-Off Valves. I install this at the campsite water spigot. One side goes to my water filter and camper’s water connection, the other side goes to the sewer flush hose/valve. I leave the camper side open all the time and open the sewer one only when emptying the tanks. It’s much easier than switching hoses around every time and avoids introducing air back into the plumbing and interrupting water use in the camper.

  • Sidewinder Hose Support. These work great to position your sewer hose over obstacles or uneven ground and flow downhill. Full review coming soon!

  • Disposable Gloves

  • Sewer Hose Seal. These help hold your sewer hose in place and make a tight connection. They’re also required at many campgrounds. 


For more detailed information about the dumping process, also see “6 Steps to Flush RV Grey and Black Tanks” and “8 Tips for Flushing RV Grey and Black Tanks