My grey water tank showed 3/4 to full after a season of usage. Before heading out this past weekend I dissolved some dawn and a cascade platinum tablet in a litre or so of hot hot water. Threw it down the sink and after driving four hours to my destination I was pleasantly surprised that my meter showed it to be empty.
Its been a few weeks since I did this. I have been at a campground in PEI and I have to say the idiot tester still seems to be working. I use Happy Camper in the black and grey water tanks. It's a little pricey but have to say it has been the best product I have used in eliminating odours and doing what ever else it does. Rv