IMO, the "Arctic Pack" heaters are not just useless, but potentially damaging. Our recently sold Georgetown had them on the black and grey tanks, which were both plastic.
According to the "fact" sheet in the documentation we got with the rig, each of them would draw 7 amps from the house batteries when switched on. They weren't very big, and I was concerned about 84 watts being applied to so small a plastic surface. Even more dangerous, there was no sensor to confirm there was any liquid in the tank. The pads had a built-in thermostat which turned them on at 40 F and off at 64 F. It was not adjustable.
Given the risk to the tank wall material, the 28 Amp draw from the 12V system of all four pads and the stupidity of trying to keep a full waste tank warm with such small heaters, I disabled them.
FR couldn't even spell "Arctic". The switch label said "Artic". To a Brit like me that's short for what is known in the US as an "18-wheeler" (in Brit-speak, an "articulated lorry").
Frank and Eileen
No longer RVers or FR owners