Nothing at all strange about it. This type of manometer measures the
difference between the pressures on the two sides. If both sides are
open, they are both receiving the same pressure on their tops
(atmospheric pressure). Push down harder on one side and the other side
goes up. Whether the hose is two feet long or 20 feet long, or whether
it has 100ml or water or 1000ml of water the same volume of water is
being lifted.
------
* That's why these are "water" column inches.

Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR

On 7/31/2007 1:54 PM neil N wrote:

> thanks guys.
>
> Strange it seems it may not matter how much water is in tube.
>
> True?
>
> I imagine a LONG column of water would change the readings. Dunno.....
>
> Anyway.....
>
> FWIW, (for newbies like me) I made the manometer with 1/2" clear hose.
> This fit over 1/2" copper pipe, but I heated the clear tube a *little*
> with a flame first. Tight fit, but it works. 5/8 ID hose would fit
> better. Use hose clamps.
>
> Make sure you use flared fittings. These are standard and I found the
> brass fitting in the  Canadian Tire plumbing section.
>
> "  3/8" x 1/2" union" : plumbing
>
> Copper fitting in pic accepts standard 1/2" copper. (i.e. for fitting
> 1/2" copper pipe to male threads of water tank)
>
> I used a little nylon tape over threads of brass piece. One could
> solder the copper and brass pieces together if desired.
>
> Cheers,
>
> Neil.
>
>