Sticky black water valve perplexes


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. 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 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 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.

##RVT779 ##RVDT1289

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1 year ago

I would suggest you make sure you have clearance before you take your valve out. Our Coachmen Leprechaun has the black and gray valves sandwiched between the black and gray tanks. I replaced ours but had to loosen the gray tank to get it back in. I would not do it again. Since then I use Super Lube and rubber gloves to coat the blade while openinjg and closing the valve. Also, if you can use an air gun spraying the blade with air seems to help. Good luck.

1 year ago

Sometimes, I have found that the problem is not with the valve itself, but with the cable (a non-kink issue). It can dry out as well. To eliminate that as a potential, drop the belly pan, remove the cable from the valve and pull out the inner cable. Squirt a little bit of 3-in-1 oil into the sleeve. This will keep it from rusting up and reduces the coefficient of friction.

Sometimes it is the valve seals. If you use a “grease” on the new seals, one product you DON’T want to use is plumbers grease. If the outdoor temperatures are warm, no problem. When temps get to about 40 or lower, the grease tends to harden.

M. Will
1 year ago

My travel trailer has enclosed tanks and valves I guess because its a 4 season trailer. You can’t get to the valves unless you take the under belly covers off. A friend at the RV repair and service shop that does my work for me recommended using Thetford RV Drain Valve Lubricant. It comes in a 24 oz. bottle and is around $7.00 on Amazon. Directions are on the back of the bottle and I really can’t say if it does work but haven’t had any valve problems. For the price its worth it to me to hopefully prevent any future problems. I put some in both the gray and black tank after every dumping.

Tommy Molnar
1 year ago

My issue is the grey tank. It’s getting a bit hard to pull and push. Our valves are up under the insulated underbelly so it’s not an easy access. Not sure what to do with that.

1 year ago

My black tank valve quit sliding because little pieces of toilet paper settled behind the valve sliding area and compacted like a kid’s papermache project. Had to replace the valve.

Ed K
1 year ago

Dow Corning is the original inventer of Silicone Lubricants. The DC-111 (Molykote is the new Brand Name) is 100% Silicone and unlike most other Silicone greases, it is NGLI-3 grade which is a lot thicker than the normal NGLI-2 grade sold else where. I use both the DC-4 on my electrical components but the DC-111 is the only way to go when doing any plumbing work. Having worked 20 years in Hospital Facilities Maintenance, I can tell when one of our workers used something other than the DC-111 when rebuilding a faucet or other valve in a water/Steam system. I will agree it is a lot more expensive than the thinner Silicones out there, but I love working on SEWAGE systems so it is a no brainer to me what I will use.

Jim Lougeay
1 year ago

Apparently Dow Corning 111 has been renamed Molykote 111.

4 years ago

I’ve used the same technique but found “silicone grease” more effective and longer lasting. A plus, no damage to gaskets from petroleum .

4 years ago

I have three tanks. A black, a grey for the bathroom and a grey for the kitchen. The first two handles are located in the water control compartment but the latter is located under the edge of the trailer. I have not had a problem with valve leaks but the handles can get very hard to pull. I use WD-40 two or three times a year. Spray it on the shaft when the handle is pulled out and work the handle in and out several times. It’s not the best lubricant but seems to work the best in this application.