did a comparison between Raritan, Groco and Jabsco joker valves and their resistance to various chemicals. Theyall did somewhat poorly with the commonly based antifreeze and this winter I stored my boat in the water and really was quite vigorous with the use of the typical product ( I forget the name but all the yards use it) at full strength. For what its worth the Jabsco valve according to PC opened 60% larger than Raritan so it was easier to pump out waste but was the most susceptible to antifreeze failure. I replaced mine on Friday with a Raritan, from Defender but next year, I will use the Jabsco as I plan to to replace the joker every spring anyway.
CLR cleanser, available in supermarkets and hardware stores, was recommended on a monthly basis for scale buildup.