My RV’s waste tank valves are starting to stick. A fellow camper suggested mineral oil to lubricate the dump valve. What are your thoughts on lubricating waste tank valves? —Charlie
I do think it is a good idea to occasionally dump some recommended conditioner down both the black and gray water tanks to lubricate and condition the rubber seal that the spade valve slides in and out of.
The Valterra gate valve is the most common model used by RV manufacturers. As you can see in the photo, it has a plastic gate or spade that slides in and out of the dump hole. There is a rubber seal on each side, which should be conditioned at least at the time of storage and a few times during the camping season.
So can I use mineral oil to lubricate my dump valve?
A lot of “old-timers” use mineral oil or even cooking oil, like vegetable oil. However, there are products made specifically for this purpose. Thetford has a great product we have used for several years called the Drain Valve Lubricant. They recommend using 1/5th of the bottle with 4 gallons of water. Mix it up by driving around some, then open and close the valve a few times keeping as much mixture in the tank as possible, then let it sit overnight. This cleans and lubricates not only the seals but the plumbing as well.
Another area that you will want to inspect is the actual lever rod and cable if you have a remote location for the handle. Many trailers will have the handle on one side and a cable running across to the tank. This can get kinked or rusted and make it hard to open and close the valve, as well. This photo shows the drain pipe bayonet with the lever just to the left and a long rod dangling with little support.
It is recommended to occasionally lubricate the rod with a dry lube such as 3-in-1 spray or CRC. Do not use WD-40 as it will remove the lubricant that came with it and is inside the housing. Extend or open the rod and valve and apply the proper lubrication to the rod and run it in and out.
One other item to inspect is the proper installation of the cable, if it applies to your vehicle. The cable should be secured within 24” and have 6” of straight cable coming out of the valve housing. See the detail from Valterra’s Installation Sheet to make sure your cable is installed properly or has not loosened up from a secure area.
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
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