Saturday, September 30, 2023


My RV’s black tank valve used to trickle when taking cover off; now it gushes!

Dear Dave, 
Whenever I dump the RV’s black water tank, usually a small amount comes out when I remove the cap. Because of this I carry a small bucket to catch the spillage. However, this last time when I removed the cap I was met with a flood of black water. Is there some way to clean the valve? I’m not even sure where the valve is, since the belly is covered. —Mike, 2020 Jayco Eagle 27.5

Dear Mike,
On a trailer like yours, the valve is typically directly at the tank and, as you referenced, covered up by the plastic underbelly. The cable comes off the valve and goes to the remote cable which you have on the side. The valve is typically a Valterra spade or sliding valve with a plastic piece that slides back and forth in a rubber gasket to open and close. Here is an example of one with the handle. Yours would have a connection, cable, and then the handle.

Click to enlarge.

Possible causes for leaky black tank valve

There could be several issues that have caused the valve to leak and most of them would be caused by the valve not closing completely. I would start by dumping some valve lubrication down the black water tank, as it might be the rubber gasket has gotten dried out. Thetford makes a product that works well. However, if it gushed out this last time, I doubt you will get lucky enough for it to be just a dried-out gasket.

The next thing would be a stretched cable, as that would be 3’–6’ long and can get stretched or loose. That would cause the plastic piece to not close completely. This would require removing part of the underbelly, which you could cut out a small section to access the cable and the valve. Then you can cover it up with a similar material. It should be corrugated plastic sheet and can be purchased at most home improvement stores. Cut a piece a few inches larger on all sides, apply silicone on the edges, and screw it to the old liner. Be careful where you place the screws to not puncture a tank or wires. Some repair locations predrill small holes and use rivets.

Check the cable

If you can access the cable, you might be able to tighten it. It may even be a broken hanger that needs to be reattached. It could also be the connection where the cable meets the handle. With the access cut, it is a good time to pull the handle in and out and watch the metal bar going in and out. If it is not moving or only slightly moving, it would need to be lubricated or even replaced. I have drilled a small hole in the top and periodically apply CRC lubricant with the straw applicator, then plug the hole with a small screw and some silicone.

You might have to replace the valve; however, an easier trick is to just install a new dump valve on the bayonet end where you connect the hose. You can get one on Amazon here. This just fits on the existing end and opens and closes. No cutting the underbelly, no messy valve replacement—just twist on.

 You might also enjoy this from Dave 

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

Dear Dave,
I am living in my motorhome because Hurricane Ian flooded my house. I can’t find the black water tank valve. However, I know where the handle is to open and close the valve, but I want to find the valve itself so I can either clean it or replace it. I have looked all over the place for it. I can’t find it in the service center like the other valves. On another topic, I wonder if I can refill the propane tank without taking it to a dealer. Thanks for your help. —Thomas, 2017 Winnebago Vista 29E

Read Dave’s answer.

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

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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.


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1 month ago

After you fix or feplace the valve you might want a clear cap with a hose connection that has a cap. With the clear cap you can see if there’s any leakage the hose fitting won’t be as messy to drain don’t ask me why I know this. Valtera F02-3106 CL EZ is what I use.

Mikal H
1 month ago

Burying valves and have long cables to operate them is a long term disaster just waiting to happen. No design should require slicing open the belly to repair or replace valves or other things that are prone to failure and critical in nature. Buyers need to be looking at these accesses and questioning them before making the final buying decision and avoid units with that design. It’s the only way we can collectively get the RV industry to design for easy maintenance and repair.

Left Coast Geek
1 month ago

rather glad my trailer (2014 Escape 21) has the valves both right at the sewer hose fitting, easy to squirt a little silicone spray in there to keep them happy. you open/close them by pulling directly on the handles of the valve shutters.

Tommy Molnar
1 month ago

This is exactly what happened with our 2012 trailer about a year after we got it. The amount of black tank water that would be waiting for me to take the cap off just kept getting worse. We had a local RV dealer replace the original valve that released with a pull of the black tank lever. That didn’t do much. We made an appointment with the mfg who added the Valterra valve and that ended any more problems with the leaking black tank valve.

1 month ago

The Valterra valve is a must-have for every black tank. Our previous trailer came with it new so we didn’t think too much of it but our current one didn’t come with one and it was a huge difference. It didn’t take us long to add one!

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