Tuesday, November 28, 2023


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 RVtravel.com’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 Nine) 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.




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Jack Fate (@guest_256336)
1 month ago

Valve itself isn’t the real issue here. Getting actually to the valve IS !

Tommy Molnar (@guest_256805)
1 month ago
Reply to  Jack Fate

Exactly right. Jack.

Buckeyebutch (@guest_256324)
1 month ago

After all the effort to R&R the valve, I’ll just replace the entire thing rather than just repair what is bad at that point.

DonH (@guest_256309)
1 month ago

There is a very simple fix that doesn’t require valve disassembly or removal. Drill a small home in the valve housing just above the handle entry hole. Squirt a liberal amount of silicone lube into the cavity where the slide goes, then close the new hole with a small screw. Run the valve in and out a few times to distribute the lube, and Voila! Any time you need new lube just take out the screw and squirt more in.

Jim Johnson (@guest_256301)
1 month ago

A few more steps on our larger RV. As part of the cold weather kit, the valves are located inside the trailer belly pan. And no there is no access hatch. I would have to make my own.

What has done the job for 6 years (and we use the trailer for 6+ months at a shot) is period treatment with Thetford Valve Lubricant (through the toilet / sink) and giving the push/pull rods a healthy dose of silicon spray. I push the applicator straw into the rod hole through the belly pan. Maintenance is nearly always easier than repair.

Tommy Molnar (@guest_256325)
1 month ago
Reply to  Jim Johnson

I think I would have to lower a good portion of the underbelly of my 2012 Arctic Fox TT in order to get to the valve. And if I went that far (which I am NOT going to do), I too would replace the whole valve like Buckeye above suggested.

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