So many tricks, tank valves made smooth!

[roady1]

I only put the oil in my black tanks. If it works good there and I see some improvement I will do the gray tank. I am thinking you could use a shop vac to blow or suck the water out of the P trap. Just be sure to let that water drain out of the tank before adding the oil. Once you add the oil use the shop vac again to blow the oil out of the P trap and into the tank. May also want to add a little water back into the P trap to avoid any smells from tank.

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[JColeman]

This is like a lot of work for what seems to me to be an urban legend. Oils float on water, therefore not getting to the parts you want lubed except when traveling through the system as a dump. Many oils are just barely liquid at room temperatures, therefore not adding to lubricity when solid at outside temps. I would be concerned about vegetable oil solids gumming up the valves.

If you are concerned about making the liquids "slippery" just put a little fabric softener in the black tank and call it a day. All this fiddling over blowing vegetable oils past p-traps is completely unnecessary.

[Cate&Rob]

The "gate" pulls back into a cavity that is supposed to remain empty . . . but, of course fills up with whatever gets past the tank side seal and into that cavity. Not practical for most because the gate valves are not accessible, but I put grease zerk fittings on my (new) gate valves and because I can get to them through opening doors in my coroplast, a pump of grease every once in a while keeps the valves working like new. See this thread and particularly the attachment to post 8. https://www.mygrandrv.com/forum/show...e-Valves/page2

Rob