REFLECTOR: Pressure testing

[Donald Royer]

I am puzzled as to why you are worried about getting a little water in your
tank. There isn't more than an ounce or two of water total in a reasonable
open U tube manometer, and about the only way you are going to get all of
it in the tank is to pull a vacuum on the tank. It will probably be at
least a year before you are going to put fuel in that tank and an ounce or
two of water will be long gone.

A one foot difference in the water level in the two arms of the tube is a
great plenty of pressure to test or leaks.

On a related note, I have often wondered why people risk using an expensive
altimeter or air speed indicator for this when a buck's worth of  plastic
tubing from Home Depot will do the job just as well.

Don Royer


>  To get this pressure with
> a simple U-tube manometer requires some care so you don't get water in the
> tank.  As you compress 35 gallons of air 1.0 psi you need to make up 2.3
> gallons.  So the best way to do this, as best I can figure, is build a
> U-tube with a 5 gallon sealed paint bucket at the bottom (paint stores
sell
> them cheap).  The paint bucket is there to provide the needed volume of
> compressed air.  Have one tube come in very near the bottom of the bucket
> (the fill tube) and the other out the top (going to the fuel tank).  The
> fill tube needs to stick straight up about 5' and the other tube should go
> up at least that far on its way to the tank (ensures no water in the
tank).
> Pour water in the fill tube.  For every 27" the water rises in the fill
tube
> you get 1 psi of pressure in the tank.
II