How to fix a sticky black tank valve

By Chris Dougherty

Chris Dougherty is a certified RV technician. Here is a letter he received from a reader while he was serving as’s technical editor.

Dear Chris,
Pulling the black water handle on my 2012 Entegra is getting more difficult compared to the gray water side. Is there any way to ease this or prevent it from getting even more difficult? —Ed

Dear Ed,
This is a common issue that black valves have over time and with repeated use. Lubrication wears off and material can get trapped in the track for the knife valve.

The best way to fix this for the long haul is to service the valve. The valve manufacturers like Valterra make seal replacement kits that are inexpensive and pretty easy to change. Once the tank is emptied, rinsed, and has been left open for 24 hours to “dry” out, you can go ahead and begin the job.

All you will need is a wrench, the kit, and a good valve grease. Dow-Corning 111 is recommended. Remove the four bolts from the valve head, and while lightly prying the pipes apart, remove the valve from the two flanges. There will be a rubber seal on each of the flanges. Remove those, taking note of how they seat in the flange.

Thoroughly clean the valve using a brush, cleaner (like Spray 9) and copious amounts of water. Look for any damage on the valve that might indicate it needs replacement. Once dry, apply the Dow-Corning 111 to the blade of the valve on both sides and operate the valve until it moves smoothly. Install the new seals that come in the kit onto the flange and coat them with the Dow-Corning 111 to help hold the seals on the flange. Then, while prying the pipes apart, slide in the valve and align the bolt holes and install the new bolts that come with the kit.

While there are other “homebrew” ways of treating sticky valves that may work for a little while, the repair I noted here will make the valve operate like new for a long time.

As a side note, you may not “need” to replace the seals; however, any kink in the seal can result in a leak. For the minimal cost, I think it’s better to go ahead and change the seals. You can also replace the entire valve for a bit more money, but I would still apply the Dow-Corning 111 to the new valve before installing it.



3 Thoughts to “How to fix a sticky black tank valve”

  1. BP

    WD 40. Spray the shaft using the straw adapter. Also buy a can of it and pour a quarter cup or so in the tank. Being water displacing it will find its way to the lowest point and will lubricate both seals on the way out.

  2. Jethro

    I’m having the same problem. I had a RV repairman look at mine yesterday. He told me the whole bottom enclosure would have to be dropped in order to just get to the valve. That only confirmed what I already was pretty sure of. I need what I call a “temp” fix about every 10 days I think!

  3. sqeakytiki

    Darn. I’m having the same sticky valve issue. And I’ve already picked up the replacement, which I fully intend to install once I get the chance.
    I was really hoping this article would have a few suggestions as to what to do to loosen that valve up in the mean time…before I get a weekend to replace it. I need to dump my tanks before I can even replace the valve and right now that’s difficult to do. Sadly this article fails to provide me with the information that I need now.

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