On my RV. I have noticed the waste gate valves have become very sticky especially on the grey tank. I'm guessing the soap and cleaner build-up are causing the valves to gum-up and stick. I poured appox. 10 ozs. of baby oil down the sink drain into the into the grey tank after I emptied the tank. The valve now slides at the touch rather than pulling and trying to force the valve close. The black tank will get treated next when it's time to drain it.
I too use baby oil or mineral oil, which ever I find first.
Papa Bob 1* 2008 Brookside by Sunnybrook 32' 1* 2002 F250 Super Duty 7.3L PSD Husky 16K hitch, Tekonsha P3, Firestone Ride Rite Air Springs, Trailair Equa-Flex, Champion C46540 "A bad day camping is better than a good day at work!"