Originally Posted by trdutch
Just make sure you close your grey valve the (last day of your trip) right before your last shower
It’s just me and My wife
Two showers worth of soapy water “flushed” out at the camp drain at tear down will keep the grey pretty clean.
It’s such a ritual for us the last night my wife always reminds me to close the grey and sometimes I actually already remember
Just like the black tanks, it is not a good idea to leave the gray tanks open all of the time.
You should let it fill and dump it when needed.
Here is an article and video about this (pay special attention around 3:00 minutes into the 5:00 minute video):
Why to keep your RV's gray tank closed when hooked up - RV Travel
My gray tank filled up last night and since I'm leaving tomorrow morning I dumped about 1/2 so I can use the gray water to back flush the black tank and rinse out the drain hose.
By the by...
To flush out the gray tank you'll just need to fill it up with water and drain a couple of times.
I've used my fresh water tank filler hose and run it through the bathroom sink drain on high force to blast water into the gray tank.