My gray water tank won't drain. While washing dishes this morning the sink started filling up. I thought at first that I had left the dump valve closed but when I went to open it it was already open...
"If 12 valve has been doing this for years, and still does not know when to drain the tanks, so they won't back up into the shower, then there is not much hope! "
NICE! Looks like the Moderator had to clean up your post, I can see why.
I don't waste my time worrying about how full my tanks are, I have a weekly routing and it works VERY WELL!!!