Tom, I agree with Allen, if you want true readings go aftermarket. I have found in ALL my past and present RV's only the fresh water level probes work. Once you get debris (i.e. wet toilet paper) across the (capacitance type) probes they tell you your tank is full and it isn't. All RV OEM's use the same brand and same junk. Great selling feature for newbies, but junk just the same. There are more expensive probes that work but no OEM RV maker will put them in for cost reasons. Then ya hear all the BS tales, put ice in on the trip home, use baking soda in the tank, fill your tsanks halfway with freash water, try brand so and so to clean... It's all BS and none of the fixes work except installing aftermarket quality probes. You may as well hold hands under a tree and have a thought trance... If you want accuracy buy and install expensive aftermarket replacement probes. What I do is use experience. Dry camping, I know we can go 2 weeks on the black and more on the grey tanks. Why not go until you max out (you'll know for sure) and then empty, then use this as a guide for your limits. JMO Tom