When camped at camp grounds do you

Standard operating procedure when camping with sewer hook-up, if we're there for only a couple of days both stay closed, we will connect stinky slinky just prior to dumping in that scenario.

Both closed until they are full enough to dump. Leaving valves open exposes tanks to fumes critters, and insects which may live in sewer lines.

(Obviously your talking dumping with hook ups. Just wanted to add that in case thread turns into a dumping post with some peoples fascination with poop)

I leave both of them closed until I dump. When we used to leave gray valve open but every so often depending on the site we would get a few odors up thru shower drain. To avoid that I keep both valves closed and give the gray tank handle a pull every morning. The black tank valve we always keep closed until we dump.

Same as you. A few days before I empty the black tank I close the valves in the two grey tanks and use that liquid to flush the hose after draining the black water.

I keep the gray open until just before the black needs to be dumped. Then allow the gray to fill some and use that to wash the hose out after dumping the black. Our black requires dumping about twice a week.

That's pretty much SOP for any of us with experience RVing

That's the way I do it also.

That's the way I do it!