Walk into walmart or Fred Meyers and get the Thetford chemicals. They have nice single packets that work well for PPs. The powdered stuff is cheaper than the liquid.. you just add a cup of water to the tank and swish it around to mix it up.
Get the no formaldehyde stuff.
Walmart is an hour away. I was there yesterday and didn't think about it so am looking for something locally, but the powder is probably something I can send away for. Thanks.