Holding tank sensors

quote=G and D]Well, here I come with another dumb question where the answer is obvious. I have found that in areas I am not yet familiar with I quite often make the wrong assumption. Sooo. In my 97 Gulf Stream Conquest there are two long tanks about 6" deep that rum from one side of the camper to the other. Im sure one is black and other is grey water.

Reading the posts it sounds like the problem with accurate readings on the tanks is caused by crud slime and subsequent corrosion. The products mentioned work to flush the yuck out and help the sensors get better readings.

My tanks on the end opposite to the dump valve each have a hose fitting. There doesn't appear to be any valve, they are just there so I assume (dangerous particularly with this application) that there must be a backflow valve. Is this fitting so I can attach a hose to the tanks and flush until clear? Would be cheaper than buying equipment I may not need and screwing on a hose is my kind of installation!

Thanks for the input
George