Whatever you do, don't give me any credit for this idea of a modification for hard to pull tank valves because all I'm doing is posting this information from another forum that someone else found on yet a third forum somewhere.  However, this guy did post some pictures of his modification along with his description of the mod.  He has given me permission to also post this information here, especially since a number of times this has been discussed.  So, without any further ado, following is the description and pictures done by David Robinson over on Suites Owners International Travel Club (SOITC), along with a question by me and an answer to that at the very end.

Terry

Black Tank Valve Hard Pull Solution

After trying other remedies for the difficult pulling valve I've tried another one. This mod did not originate from me but rather on another forum but I have done it and can show you what it took to do. Basically it's installing a grease fitting in the plastic valve section where the valve blade retracts to when dumping. Each pull of the valve to open pulls the blade back into the grease and lubricates the blade. When closing the valve the grease lubes the rubber gaskets on it's return.

Due to the valve location I had to remove it to work on which of course requires dumping the tank and a generous flush cleaning. First raising the door side to completely empty the tank and then lowering the door side to stop anything left from leaking out.

Remove the four bolts (wear gloves) don't drop the nuts, and pull the valve out. There was plenty of slack cable to pull the valve out to the storage area. With the valve closed I drilled a 7/32 hole in the bottom flat part near the three inch hub adapter. The package of grease fittings I bought had and assortment of straight, 45*, and 90* fittings and I chose the 90* one based on the valve access for applying the grease.

I did not have to tap the hole as there is little chance of liquid entering that area and leaking out through the threads. Just start a number 8 machine screw into the hole to start some threads then screw in the new grease fitting.

I purchased a small pistol type of grease gun with three small grease cartridges called Green Grease which is a synthetic polymer grease and is waterproof. Do not use petroleum based grease as it will cause the valve seals to swell.

While the valve was still out and open I pumped in enough grease to see it coming out around the valve blade then outside I worked the handle in and out to lube the blade.

Reinsert the gaskets into the flanges or the valve itself and reinstall the valve with the four bolts tightening only snugly.

Outside open and close the valve a few times to lube the seals. Test for leaks and you’re done.

So far this mod has worked better than the previous ones mainly the veg oil and GEO.

Note that in the pictures there is a screw plugging a hole from a previous attempt to shoot in some spray lube to ease the pulling force required. That one also failed to work. The last picture shows the grease fitting about in the middle of the picture. Still pulling the handle with two fingers.