Sunday, May 28, 2023


My RV’s black tank flush valve leaks, and the tank valves are labeled wrong!

Dear Dave, 
When I use the black tank flush connecter on the outside of the trailer, I get water flooding the inside. I cannot verify where exactly, but I believe it’s from under the sink in the bathroom cabinet. Until corrected, I’ve been using a Camco 39080 tank rinser to attempt to flush the tank, but unsure of its effectiveness due to the bends in the combined gray/black hose connector. I bought this trailer a year ago and learned the hard way that the gray/black drain valves were labeled backwards. —Andrew, 2011 Heartland 30RKDD

Dear Andrew,
From what I can find on the walkaround videos, the black water tank of your Heartland trailer is installed under the main floor inside the outriggers with an underbelly material similar to a plastic corrugated cover. The bathroom is designed just before the front bedroom on the driver side of the rig. However, the toilet is placed almost in the middle of the floorplan. This would mean the black water tank is somewhere either directly underneath or just offset with a 45-degree-angle pipe coming off the toilet.

Black water flush valve

The black water flush valve is a through-the-tank valve mounted to the side close to the monitor probes. It spins pressurized water from an outside source at the probes and cleans the side of the tank and the monitors to reduce inaccurate level readings. Since your tank is in the middle of the floorplan, it has a remote connection on the side of the rig and a hose going to the actual valve. I cannot tell where the connection is exactly from the videos. However, I do see some type of connection on the driver side between the two slides and another on the back wall. One of those would be the city water connection, which I assume would be the one on the back.

In either case, you hook up an exterior garden hose to the female connection on the side of the rig and pressurized water flows through the connection and a hose that is routed to the actual valve. Most RV owners don’t realize that this hose needs to be winterized if the unit will be exposed to freezing temperatures. It will have water sitting in it and if it freezes it will crack and leak, like you are experiencing. You will need to remove the underneath cover to follow the line and find the leak. You may also need to remove the bottom panel in the cabinet. You’ll find that most RV manufacturers don’t design these for easy access!

Flush wand not as effective as valve

I agree that the flush wand you are currently using is not as effective as the valve, as you stated, because of the potential angle of the drain pipe and the location of the probes. Here is one that we have used in some of the videos. You can find it on Amazon here.

Plus, it’s a pain to use as you need to run a garden hose into the rig and stick the wand down the toilet and then pull it out and have the wet wand that now needs to be taken out of the rig. Yuck! I would take the time to track down the leak and get it fixed. I would also suggest using Thetford Tank Blaster periodically to clean the entire tank.

Tank valves labeled incorrectly

Regarding the black and gray water valves being labeled incorrectly, keep in mind this is a 2011 model year and probably built in 2010, an economic low point in the RV industry. Most RV manufacturers had shut down operations periodically or for long periods and laid off employees. Then when operations would start up, off and on, skilled employees were reluctant to return. So, what you got was line workers that did not know a black water tank from a freshwater tank—which is scary!

Typically, the drainpipes, valve handles, and bayonet connections are located beneath the rig, like in this photo, rather than in a compartment.

The actual valve is underneath the corrugated underbelly with the valve sticking out, like this one. Even if the valve is labeled incorrectly, you should be able to verify what valve opens what tank by looking at the corresponding drainpipe. I tell owners that we have a responsibility, as well, to learn how the systems work and not rely on dealers or manufacturers. Also, I recommend owners read their manuals and any educational material they can get their hands on. In this case, the handle opens the valve for the gray water tank, as the drainpipe is a smaller 2” pipe. Above, you see the drainpipe on the left side is 3”, which is larger for the black water tank and valve, as it will have more sludge and toilet paper.

I’m not defending the manufacturer. However, since this is a 2011 model, the dealer should have caught this or the previous owner of the RV. Hopefully, you have corrected the labels for the next owner!

 You might also enjoy this from Dave 

Ask Dave: I want to clean my black tank valve but I can’t find it

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


We have a popular forum for Ask Dave. Please be as brief as possible. Attach a photo or two if it might help Dave with his response. Click to visit Dave’s forum. Or send your inquiries to him using the form below.

Click or drag a file to this area to upload.


Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


5 8 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
1 month ago

The leak is probably a vacuum breaker installed high in the sink cabinet.

Terry C
1 month ago
Reply to  TIM

This. We had a stink bug crawl into ours and kept it from closing tight. At least it was fresh water.

Tommy Molnar
1 month ago

When our 2012 travel trailer was new, the black tank valve always leaked so when I would twist off the outside cap, some ‘stuff’ would spill out. I had a local dealer replace the tank valve under warranty (not the dealer I purchased the trailer from). It still did the same thing. When we went to the mfg in OR for some other work, I complained about this. They simply installed a knife valve at the outside of our dump connection and that fixed the problem for good.

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.