Gray Water Tank Gauge?

We finally went for a real camping trip in our new-to-us TM 2720 and I have a couple of questions that I can't find the answers to anywhere. I'll post them separately, since they are totally different topics.

How do I know how full the gray water tank is? It looks as if there is a gauge under the kitchen sink, but it never changed. Is there something I'm supposed to do to turn the gauge on?

I can't even quite tell where the tank is, but when we emptied it, there did seem to be a lot in it - four days worth of dish and hand washing. I think I need a pictorial tour of the guts and underbelly of the TM!

The left most button on the display is labeled TEST. Push that to display the level of the holding tank and the fresh water supply. If you are not drawing any power off of the batteries and are not plugged into shore power you can also get an idiot light display of the battery state. Most of us use either a volt meter or a battery monitor to keep an eye on the battery.

fwiw, I find that we use about 5 gallons of water per person per day, including a navy shower every other day and a sponge bath in between. This is with 5 adults camping for a long weekend.

If you over fill the gray water tank, it will backup into the shower. This will not cause a problem unless you use the shower tub as a hamper, which explains why I know this.

Some owners have had a problem with water leaking out of the top of the TM gray water tank on to the ground when it is overfull. This seems to be caused by the top pipe fitting not being properly attached. This only causes a problem when over filling the gray tank.

Thanks, Wayne.

It surprised me that there wasn't anything in the owner's manual about that test button, and didn't want to just push random buttons.