Click on Image Gallery for detailed blueprint and diagram.
Jim Amdal explains a method
that will allow you to measure—easily and
accurately—the amount of water that your big elevated
storage tank contains. The project, says Jim, should cost
you no more than $10 and two hours.
Determining how much water I had in my water tank used to
be a real chore (what with having to climb the tower in
order to peer through the tank's manhole) ... until I
devised a painless—yet accurate—way to check
the container's water level while I stood on the ground.
The answer? A simple sight gauge which uses the compression
of air in a length of clear plastic tubing as an indication
of water pressure ... which-in turn-is nothing but a reflection of the tank's water capacity.
The accompanying drawings will give you an idea of how the
system is set up. As you can see, there's nothing complex
about the gauge's construction (I built mine in two hours
at a total parts cost of less than ten dollars ... and I'm
sure you can do the same). About the only slightly thorny
part of the whole project is the calibration of the
sight-tube ... and even that's a snap when you know how.
 First of all—with the plug (Part 1) removed from
the top of the transparent plastic tube—open the
shut-off valve (Part 2) just a crack, until the water level
is visible near the bottom of the sight gauge. Close the
valve, replace the plug, and tighten the top hosing clamp
until air will no longer escape past the end plug. (Hint:
Some air loss is virtually inevitable, but you can cut that
loss to an absolute minimum by giving the tubing plug a
light coat of very thick grease prior to installing it for
the last time.)
 Drain the tank ... but not the service pipe. Now open
the shut-off valve and you'll see the water level rise in
the plastic tube as a result of the head pressure created
by the water remaining in the service pipe. Mark the
position of the meniscus, or water level, on the plywood
backboard and label this spot "TANK EMPTY". (Leave the
shut-off valve open from now on.)
 Next, fill the water tank brim full. Then mark the
position of the meniscus on the backboard and label the
spot "TANK FULL".
 Find the midpoint between the "TANK FULL" and "TANK
EMPTY" lines and mark this locus -1/2 FULL". Make as many
other subdivisions of the scale as you feel necessary.
The usefulness of this gauge is not limited to water tank
systems alone. It can also be used to measure city water
pressure, and—by acting as a pressure-overload
damper—can even cure water hammer problems.
In addition, if you have your own water pump, the makeshift
pressure indicator can help you detect pump failures, line
breaks, or even a drop in the water table (should this
affect your pump's pressure output).