Mine is the same as JimToo..
One thing you can do to check the valves out, is close all the valves. Run water into the sink (use a water hose from outside) and fill it up until you get water into the sink. Go out and pull the #2 valve and if a lot of water comes out you know it is the correct tank.
This will also help you check it out for leaks. I was leery at first but do it quite often to make sure any debris that may be in the tank is washed out.
I also do this to the shower and black tanks.
Thats what we do...
BC