debris in grey tank

I had the same problem with my sensors and no visible way to clean them in the gray water tank and tried most of the chemical approaches with little to no luck. Then, I saw a drain plug on the bottom of the tank which was, I think, a 3/8" sized pipe plug. Removed it and made a tool out of the metal pipe that connects a toilet angle valve to the bottom of the toilet's water tank. I fastened an adapter for a garden hose on one end of the metal pipe, soldered closed the other end and drilled a hole like maybe 3/16" on one side. Now all I have to do is insert this tool up the drain hole, turn on the water and the water blasting out the side hole REALLY cleans not only the sensors but also the whole tank and you'd be amazed at how much water pressure comes out of that little hole. It flares out to a steam at least 6". I leave the dump valve open so that it'll drain the waste water and I hold a rag around the metal pipe where it enters the tank. Works great! First time I've had to clean this tank in 5 years and hoping to not have to do it again for a long time. Try it you'll like it!