Water level manometers certainly do exist. I frequently see pressures measured in inches of mercury (Hg) or inches of water. The beauty of it is you can make your own manometer quite easy and use inches of water column if that is how you would like to measure pressure.

I wouldnt use it for a home inspection though. Its great for measuring extremely low pressures (less than 1 bar). Mercury measurements are much more precise though when you get down to the RCH.