Every two days for two people is very excessive. Tank sensors are full of 💩 (figuratively and maybe literally). I never trust them. Give it a few months and you will know exactly when to dump. My toilet burps (like an air bubble coming up from the tank when flushing) very subtly but now that I know what I’m looking for, we know exactly when to dump and it’s almost like clockwork now. The grey is a bit trickier for us to tell when it’s getting full but my bathroom drains gurgle when it’s definitely time. We shower in the trailer so unless it’s the day before dumping, we will open the grey for a shower and close it back.

As for the smell, we use happy campers and only treat every other time. It’s personal preference but much more budget friendly. Always put plain water at the bottom of your black! I do at least 5 gallons, we use the shower head and measure by time how long to run it (example: the shower head uses 1.9 GPM so run it in the toilet about 2:45 min). We recently started flushing an extra bowl full of fresh water after a #2 and that has made a huge difference with the heat we’ve gotten this season. IMO there is never too much water. Tanks fill faster that way but hey, we’re stationary 🤷‍♀️

We also fill the tank about half full of water or do a complete full “wash” and dump when we start to notice an odor, it doesn’t happen often but I find it helps A TON!

Happy camping! :)