Originally Posted by Derek700
If I know we are going to a site with sewer hook up I put about 5 gallons of water and some laundry soap in the black tank and just dump it when we get to our site.
My mode has been similar on boat holding tanks except that I use very cheap brand powered diswasher soap. It has many of the same ingredients as more expensive holding tank chemical additives (sodium carbonate being one) and doesn't foam like laundry detergent and hand dishwashing soaps. Foaming is more of an issue on boats. I don't buy any expensive tank specific products. I find that dishwasher powder works against odors very well.
I'm going to add the bag of ice procedure I've read about here. The ice should safely rub some of the residue clear. It seems to be a good idea.
As an aside, if you ever have someone put hand dish soap in a dishwasher you will find that it foams and suds all over to make a real mess. To try and clean or dilute it out using more water is not very effective. Knowing the anti-foam properties of dishwasher soap I learned to just add some more proper powdered dishwasher soap to the foaming mess. It is counter-intuitive to add more soap product to that situation, but it works to knock the foaming right down in the next cycle.
I learned to do that at a bed and breakfast which I maintained, but that information has also helped some friends who had someone use the wrong soap (aging parents, children, etc.). At first they resist the idea of more soap, but it works every time. FWIW. vic