Are you talking about a self watering container where you want to know how much water is in the reservoir or a regular container?

If a regular container you do not want standing water at the bottom of the container. This should all drain out via the drain hole.

If a self watering container the easiest method I know of is to install a water gauge. A simple PVC tube as you described will work. Next use something light weight with good buoyancy such as a piece of foam or styrofoam cut to fit. Fill the reservoir to the top and insert the foam. Cut the foam off so it is flush with the top of the PVC tube. This is your full indicator. As the water level drops, so will the foam. An alternate method is to measure the height of the reservoir and cut the foam off that much higher than the top of the fill tube. When the foam is even with the top of the tube the reservoir is empty.

Thanks so much! Great ideas and exactly what I was looking for!
~Tom

I use a self watering container and have the tube as you said yours is. I did just as justaguy2 said to measure the water level, but soon found out that to drill a 3/8 inch hole in the side of the container next to the pipe and at the level you want the water. Then allyou have to do is put water in until it comes out the hole, its full.

I do the same as you do, Ruthndan, with regard to the overflow hole.

If one has a lot of container plants it is a pretty safe bet that something needs watering on any given day so why not stick the hose in the fill tube and top things off?

At the same time I do enjoy the luxury of a water level indicator too.

To each their own! ;-)

justaguy I still have 3 of the measuring sticks I started with and also use them sometimes, You know just check a few pots to see if I need to pull out the old hose. DAN

justaguy2 you have seen me as ruthndan but there a mistake that is hard to figure out, now I am back as dangsr-grow so I hope you will know me by this name from now on. DAN

mental note filed, dangsr ;-)