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RVers often ask us how to get rid of sticky black water holding tank valves — in fact, the subject comes up so frequently that we decided to create a quick guide to help.
This guide covers the following key topics about black tank valves:
- What Causes Black Tank Valves to Get Stuck
- How to Fix Sticky Black Tank Valves
- How to Prevent Black Tank Valves From Sticking
Why is My RV Black Tank Valve Sticky?
There are two main reasons that a black tank valve can be sticky:
Sticky Black Tank Valve: Debris After Dumping
When dumping the black water holding tank, we often let everything flow out of the tank all at once, and then get back on the road without properly rinsing the tank. Maybe it’s because there is a line at the dumping station, or maybe you just need to get on the move.
After closing the black tank valve, anything that was left behind from that initial dump can get pushed into the pathway where the knife blade is located, and can get stuck between that and the gasket which seals it off.
As you let the RV sit, either while not in use or while you’re driving, air dries out everything around the black tank valve, which can make the valve feel sticky.
Sticky Black Tank Valve: No Shaft Lubrication
The other reason you can experience a sticky black tank valve is from the shaft itself. The shaft is what allows you to open and close the black tank valve by pulling it open.
The shaft of a black tank valve is a lubricated piece, and if it is no longer lubricated, it can become very difficult to open and close the valve.
How to Fix a Sticky RV Black Tank Valve
If you’re dealing with a sticky black tank valve, we have some expert advice about how to fix the problem.
Step-by-step instructions for how to fix a sticky RV black tank valve:
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Fill the Black Water Holding Tank With Fresh Water.
One of the best ways to break debris that may be causing the black tank valve to stick is to fill your tank completely with fresh water.
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Crack Open the Valve.
Make sure that the water line is well above the discharge port, and gently crack open the valve, approximately ¼” in the pole, and then slowly open the valve. This process will force water through the smaller opening, and can help break the debris that is built up inside of the tracks, and across the blade itself.
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Work the Valve.
Once you have the blade fully open, work it back and forth several times while water is still rushing through. This will allow any lingering debris to be broken free from the track of the blade, removing most of the problem.
Sometimes, simply allowing water to run through isn’t enough to clear built-up debris in the gasket chamber in between the knife valve and the rest of the assembly. If you’re still struggling with a sticky black tank valve after following steps 1-3, proceed to step 4.
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Connect a Secondary Valve.
In order to clear heavy build up, we highly recommend placing an additional bayonet-fitting knife valve on it so you can shut off water flow, preventing water from leaving the tank and the original black tank valve assembly.
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Add Water to the Black Tank.
With the original valve in the open position, and the added valve in the closed position, add water to the tank so that it fills the space between the two valves completely. This may require quite a few gallons of fresh water.
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Pour One Bottle of Unique Clear-It Into the Black Tank.
Once everything is submerged, we recommend adding a bottle of Unique Clear-It into the black water holding tank through the RV toilet, and allowing it to sit for as long as possible. Sometimes, Clear-It can remove waste build-up overnight (8-12 hours), however, if the build-up is significant, it may take a full 24-72 hours.
There is no time limit for Clear-It, in fact, the longer you let Clear-It work, the better your results will be.
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Work the Valve Again.
Before you open the secondary valve to dump, we highly recommend moving the original valve back and forth a few times to help clear out anything which might be stuck in there.
Usually, this process is enough to break through any debris and toilet paper that may have been stuck in the path of the knife valve.
What Happens if Your Black Tank Valve is Stuck Open?
We’ve also had customers ask about what to do if their black tank valve is stuck in the open position.
If You Have Access to the Black Tank Valve
Start by rinsing the gasket area with a garden hose with a spray nozzle, or by placing your thumb over the end of it to make it spray, which can knock debris loose that is caught in between the gaskets.
Alternatively, you can pour Dawn Ultra liberally in between the gaskets, which can lubricate the valve enough to free it up.
Lastly, you can opt to replace the valve itself. You will need 2 wrenches to loosen the screws from the backing nuts. While leaving the original part attached to the RV plumbing, you can replace the two seals and knife valve assembly. Be careful when aligning the seals so they do not get pinched.
If You Don’t Have Access to the Black Tank Valve
If you have a black tank valve that is operated through a wet bay or with a cable system, we recommend following cleaning steps 4-7 above, and utilizing a secondary valve, Clear-It, and plenty of water.
However, because these types of valves can be difficult to access, you may need to hire a certified RV technician or visit an RV service center to fix the problem.
If You Can’t Get Your Black Tank Valve Handle to Move At All
Sometimes, when valves are left alone for long periods of time, they can dry out and seal themselves closed.
If your black tank valve is completely stuck, you can gently press a plastic pry tool along the gasket with the valve closed, with the tool positioned between the gasket and the knife valve face. Then you can spray a mixture of water and Dawn Ultra dish soap into the gap.
We also recommend trying to spray silicone dry lube on the shaft of the pull handle, as well.
Once you are at a full hookups campsite or dump station, slowly attempt to work the valve open. It helps to move it slowly back and forth with the handle.
After the valve is open and the tank has been drained, spray water directly into the gasket gap that the knife valve sits in to make sure it is fully cleaned out.
To learn more about using your black tank valve properly, read our guide: Why It’s Crucial To Keep Your RV Black Water Valve Closed
Still Need Help With Sticky RV Black Tank Valves?
If you’ve followed the steps we provided to fix sticky RV black tank valves, and you still need help, don’t worry, we’ve got you covered.
Reach out to the Customer Service Team at Unique Camping + Marine for friendly and professional advice about your RV black tank valves. Our experts can address your specific concerns, and help you get back on the road with confidence.
How to Prevent Sticky RV Black Tank Valves
When it comes to preventative maintenance, we have a few helpful recommendations.
Preventative Measure: Rinsing the Black Tank & Knife Blade
For best results, we recommend thoroughly rinsing your black tank after every dump by filling your black tank completely with fresh water, and then dumping. You should repeat this process 2-3 times to remove lingering debris from your black tank.
This rinsing process moves water past the gaskets, and the knife blade itself, and should prevent debris from getting stuck and drying in the valve.
Learn why rinsing your black tank thoroughly is one of the best things you can do for your RV:
Preventative Measure: Lubricating the Shaft
If you just need to lubricate the shaft of the valve itself, we recommend applying dry lube occasionally to help keep it moving freely. It is important to use a dry lube, and not something like WD-40, because it can attract a lot of dust that can actually build up inside of the chamber, which is much more difficult to clear.
Whenever you lubricate the shaft, make sure you work it back and forth with an empty tank several times in order to make sure it's sliding easily like it should.
No More Sticking Points: RV Black Tank Valves Restored
Sticky RV black tank valves can make dumping your tank harder than it should be. Whether the stickiness is caused by debris build up in the gaskets or lack of lubrication in the valve shaft, a few easy steps can help fix the problem.
By properly rinsing your black tank after every dump, and keeping your valve shaft lubricated, you can avoid the headache that comes from a sticky, or completely stuck, black tank valve.
If you want more in-depth information on black tank valves, watch this video: Take Apart an RV Holding Tank Knife Valve: How it Works!
Prevent Common Problems In Your Tanks!
From misreading sensors, preventing clogs, or eliminating odors, we've got you covered no matter how you camp! All our best holding tank tips and trick information plus more can be found conveniently in one place when you download our FREE Unique Method Field Guide PDF. Achieve holding tank bliss today!
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