Thursday, December 8, 2022


How to lubricate sticky RV dump valves


By Doug Swarts
We’re asked often about the proper method to lubricate a sticky RV dump valve. The RVers are usually referring to the black 3-inch gate valve on their black holding tank. In some cases the 1.5-inch gray valve gets sticky over time especially if the RVer is not using his RV full time. The contents inside the valve dry out causing the valve to stick.

Empty and clean your tanks by filling the tanks 2/3 full of water then dumping, repeat until the clear view fitting at the sewer ground inlet runs clear and free of particulate. Next, remove the valves from the flanges that hold them in place in the piping. Detailed instructions can be found here. (Note: These particular instructions are for our Drain Master electric valves where you can submerge your manual valve completely.)

Soak the valves in hot water with some detergent, making sure to leave the gates open. Periodically agitate the valve with the open or hole end down in the water – the idea is to remove the debris that collects in the body of the valve over time as the gate is opened to dump your tanks. When you feel the inner body of the valve is clean, remove and blow the inner valve body to remove any excess particulate that air pressure may loosen. Use Dow 111 synthetic grease or any non-petroleum grease and lubricate the SS shaft if your valves are the manual pull type. Close the gate and apply a thin coating of grease to both sides.

Remove the seals from the flanges and inspect both of the seals and the flanges for cracks or abrasion. If damaged, replace.

Apply a thin coating of grease to the seals and install them on the flanges. Holding the piping/flanges apart, insert the valve between the flanges being sure NOT to move the seals. Squeeze the flanges together and insert the four bolts and nuts. Make sure to hold the flanges tight against the valve during this process. Now finger-tighten the four bolts/nuts then use a wrench and tighten them to 20-inch pounds of torque OR no more than 1 1/2 full turns. DO NOT OVERTIGHTEN!

Install a grease zerk or access port so the valve can be lubricated without removing the valve. We have heard from a number of our customers that speculate this would be the answer to solve their problems once and for all. If you plan to attempt this we highly recommend you put the hole in the thickest part of the valve which is the TOP or where the SS shaft comes out of the body when you pull on it. The thickness will allow you to tap the body with enough threads to screw in a plug or grease zerk. Drill your hole in the center of the left or right side of the SS shaft hole, approximately 1/2” from the SS shaft.

If you use a grease zerk be sure you do not apply too much grease or the valve will be hard to pull and push open or close. A plug would work better as you can spray silicon spray into the hole then plug it again.

If your valves are installed in the tank piping with the handle lower than the 3 – 9 o’clock position when you open the valve the water inside will seep into the valve body (the root cause of sticky valves). IF possible, reposition the valves so the valve body is above the 3 – 9 o’clock position so the water that seeps into the valve body will drain back into the bottom of the pipe.

Most RVs with cable pull or rod-actuated valves are positioned in the side or 3 o’clock side of the exit pipe, allowing this contaminated water to lay in the bottom of the body and creating this issue over time.

Doug Swarts is a 25-year RV industry expert at creating and implementing revolutionary products for all RV waste management systems. His sound principles of RV waste management have led to a group of products designed to make the unpleasant task of dumping holding tanks more sanitary, safe and convenient for the end user. Doug is the founder of Drain Inc., Hollister, CA, which sells as well as installs Drain Master, Waste Master, 360 Siphon, HepvO and other RV waste-related products. 


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Wayne R
1 year ago

I agree with Gerald. I’ve been an auto mechanic for 43 years, and never heard them called anything but “ZERKS”. What the heck is a ZERT??? …maybe a zit, but that’s another problem for my teen years

RV Staff(@rvstaff)
1 year ago
Reply to  Wayne R

It’s been corrected. Thanks, Wayne and Gerald. 🙂 –Diane

4 years ago

Oh, for goodness sakes… we have a 2000 Sunnybrook travel trailer and when our grey/black tank dump valves become harder to pull, we simply spray the metal rod connected to the T handle with silicone spray (NOT WD 40). Pull the T handle all the way out, spray the metal rod, slide it in, pull it out again, spray the metal rod, slide it in, etc., etc.
Repeating this 6 or 8 times for the black dump valve and the grey dump valve solves the problem. Sometimes a simpler solution is all that’s necessary. Keep your tanks flushed out with clear water as often as possible. We full-timed in our Sunnybrook for 7 years and on the rare occasions we had a full hook-up site, we flushed those tanks within an inch of their life. We also stayed almost exclusively in Forest Service / National Park / Corp of Engineers parks and never put any “solids” in our black water tank. That’s what campground bathrooms are for. Also never put any solids or organic matter down our kitchen sink so our grey tank stayed odor free. Just wipe all dishes/ pans/skillets out completely with paper towels (first dry, then wet) before washing them.

4 years ago

If I’m going to pull off the valve I would probably replace it unless I am in a location that I must repair. I have replaced both gray water valves on my TT because of too much glue during construction. They did work but were very hard to pull out and push in.

4 years ago

I use a couple bottles of vegetable oil in the black water tank,after flushing well,then open and shut the valve quickly.Never had a problem with sticky valves since.

4 years ago

Any suggestions for enclosed tanks and valves? I’ve got a sticky gray valve but can’t get to it as it’s enclosed. The RV Proctologist gave my tanks and valves a good cleaning but the gray is still difficult.

Tom Hargreaves
4 years ago

I’m afraid I’d be very tempted to simply buy a new valve and lubricate it during installation. If the upstream side of the valve is glued to the pipe, I’d disassemble the valve then determine if it’s feasible to replace with most of a new valve. (I guess I’m not a big fan of working with _____. And no i probably wouldn’t make a good mother. )
In addition, after cleaning the tank, i would try to tilt the rig away from the valve to preclude that last bit of “water” from escaping.

4 years ago

I assume you prefer the pull to be in the 12 o’clock position which would be straight up. Pretty hard to pull upwards when the compartment ceiling is in the way!

gerald fuller
4 years ago

I think they are called zerks

Rick Myers
2 months ago
Reply to  gerald fuller

I have heard both ways over the years, might depend on where you are from