The sensors on our tanks are on the outside of the tanks, no penetration. When we got the coach it was set up with a grinder pump and a 1" drain hose. A lot of people on here swear by these and while they do work as designed it is a slower draining than the stinky slinky. Any way I switched over to the 4" hose as I do not to pump uphill. A scale had attached itself to the side walls and stopped my gauges from detecting the fluid inside the tanks. I attribute this to the SLOW draining using the pump. I filled my tanks with about 1/4 to half full, a guess as I had no gauges and added 1/2 of Dawn dishwashing liquid into each tank. 9 oz bottle not much. 60g Gray and 40 gal Black. I did use hot water. I drove around a long block 8 miles. and let it set until we went camping the next weekend. Went camping 45 miles dumped the tanks and they have been working flawlessly since. Still working great and it has been several months and several tanks full. Try it, it worked for us and pretty simple. Larry