Thursday, October 6, 2022


What to do about 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 the sticky black tank valve from getting even more difficult? —Ed

Dear Ed,
This is a common issue that black tank 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. 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. Molykote 111 from Dow Corning 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 Molykote 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 Molykote 111 to help hold the seals onto 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 tank 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 Molykote 111 to the new valve before installing it.


How to lubricate sticky RV dump valves



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1 year ago

When I dump my tanks, first I always have a small section of clear pipe mounted before the hose so I can watch the contents discharging through the dump hose. Next I always dump the black tank first. Once that tank has been emptied I leave that valve open then open the gray tank valve. Once the waste water gets close to finishing there will be generally soapy water. That’s when I then close the black tank valve using the soapy water as a lubricant. Then close the gray tank valve and that will be lubricated with the soapy water. I put new valves in back in 2008 and I haven’t had ANY sticky or leaky valves ever since then.

Dave Czarnecki
1 year ago

Most of campers with concealed valve locations are cable operated. My experience with a “sticky valve syndrome” actually turns out to be a “sticky cable issue”. I remove the cable pull handle and cable mounting nut to get better access to the cable end/opening. I spray lubricant into the cable end/opening while holding the cable up so the lubricant drains deep into the cable. I work the cable back and forth open/shut while adding more lubricant. So far, this has worked every time.

1 year ago

QUESTION: The valve might be easy to lubricate BUT, my 5er underbelly is covered. Am I going to have to cut the covering to access the valve?

Tommy Molnar
1 year ago
Reply to  Dave

Good question, Dave. Our travel trailer also is covered and there’s no way to even SEE the valve. Now it starts to sound like a REAL project – that I will pay someone to take on.

1 year ago
Reply to  Dave

What the hell were the design engineers thinking or better yet LACK of THINKING when they put that design together?

Lorraine A Gehring
1 year ago
Reply to  Dr4Film

They were thinking to insulate the valves from colder weather. Our Class A has a covered underbelly, as well as a wet bay with a plate that has to be removed if a new cable is needed.