RagtimeDon... I'm from Columbia MO! But we keep the boat in Annapolis. Just this week a J42 arrived at our dock and the owner is from St Louis! MO does have sailors! I was taught to use vinegar and also flush a bit of mineral oil from time to time. Mineral oil to lubricate the rubber gaskets and to assist the "movement" through the hose to
holding tank. Vinegar to break down salt and uric crystals. You can purchase from a camp supply store the poop in the woods kit. Which for some reason I thought would be a good idea to have on the boat in case the head malfunctioned. The bags that came with the kit turned to dust over a years time-thank goodness we didn't need them. I also put one of those clip on toilet cleaners on our head bowl. I don't use the ones with bleach in them. And I agree with above about flushing fresh water through the head before leaving the boat.