ENGINE DIAGNOSTIC TOOLS Section 4 DWYER SLACK TUBE® MANOMETER DESCRIPTION The manometer (Figure 13) is a "U" shaped tube with a scale  mounted  between  the  legs  of  the  "U".  Where  the portability of the SE-2239 is not required, this manometer can be used to measure either low pressure or  vacuum and  may  be  filled  with  water  or  mercury.    The  Dwyer Manometer  filled  with  mercury  can  be  used  to  calibrate the 0-30 psi gauge of the SE-2239. Figure 13.  Slack Tube Manometer "A" Dimension Indicates Total Fluid Column Dwyer No.  121148 Order from:    Dwyer Instruments, Inc. P.O.  Box 373 Michigan City, Indiana 46360 Phone: (219) 872-9141 FILLING The  manometer  may  either  be  filled  with  water,  when checking   very   low   pressures,   or   with   mercury,   when checking    slightly    higher    pressures.        Refer    to    the Performance   Data   Guideline   pages    in    Section    6    to determine whether water or mercury should be used. When  filling  with  water,  use  only  good  drinking  water without     additives except for some colored water vegetable dye which enables the tester to read the scale easier.    With  both  legs  of  the  manometer  open  to  the atmosphere, fill the tube until the top of the fluid column is  near  the  zero  mark  on  the  scale.    Shake  the  tube  to eliminate any air bubbles. When using mercury, the quantity of fluid needed may be found  in  the  Operating  Range  and  Mercury  Fill  Chart. Use triple distilled mercury to minimize tube discoloration. IMPORTANT NEVER USE AN ANTI-FREEZE SOLUTION, SODA POP,  TONIC,  ETC. THE INCREASE IN DENSITY CAUSES FALSE READINGS. OPERATING RANGE AND MERCURY FILL CHART Required Operating Ounces Tool No. Range of Mercury Inches of Water or Mercury Dwyer No. 1211-48 24"-0-24" 22-1/2 INSTALLING AND READING 1. Support the manometer in a vertical position.  Be sure the fluid is at the zero mark on the scale. 2. Connect one leg of the manometer to the source of  the  pressure  or  vacuum.    Be  sure  the  other leg is open to atmosphere. 3. Start  the  engine  and  when  the  engine  is  in  the proper     operating     condition     as     specified     in Performance Data Guideline pages, observe the manometer. CGES-240-4 Printed in United States of America Page 18