Reading Your Manometer & Checking Draft Pressure

Periodic Maintenance & Calibration: 
Manometer Inspection & Zeroing Calibration

A properly calibrated manometer is your first line of defense in maintaining safe, balanced airflow and maximizing filter life within your spray booth. This guide provides step-by-step instructions for inspecting, maintaining, and zeroing your Mark II inclined manometer.

Step 1: Visual Inspection & Housing Maintenance

Before adjusting the gauge, ensure the physical assembly is clean and structurally sound:

• Check the Fluid Level: Verify that the red gauge fluid is sufficient and clearly visible in the reservoir. If the fluid level is low, it must be topped off before attempting calibration.

• Inspect the Tubing: Examine the plastic pressure lines running from the booth plenum to the manometer. Look for kinks, cracks, or clogs caused by overspray or debris. Replace any damaged tubing immediately.

• Clean the Exterior: Wipe down the exterior faceplate of the manometer with a damp, lint-free cloth to remove any overspray or dust that might obscure the scale or block the vent holes.

Step 2: Zero-Pressure Alignment (Calibration)

To get an accurate reading of the static pressure across your filters, the manometer must be zeroed while the spray booth is completely powered off.

1. Shut Down the Booth: Ensure the exhaust fans and Air Make-Up Unit (AMU) are completely turned off. Wait for the fan blades to come to a total stop so there is zero airflow or static pressure in the booth.

2. Vent the Tubing: Disconnect the plastic pressure tubing from the top of the manometer to ensure both sides of the gauge are vented to the exact same atmospheric pressure.

3. Locate the Zero Adjust Knob: Find the black thumb screw/knob located at the bottom of the manometer housing.

4. Align the Fluid Meniscus: Turn the adjust knob slowly left or right. Watch the red fluid column move along the scale until the bottom of the fluid’s curved surface (the meniscus) aligns perfectly with the 0.00″ w.c. (Inches Water Column) mark.

5. Reconnect the Tubing: Once zeroed, firmly press the plastic pressure tubing back onto the manometer’s molded connectors.

Step 3: Verifying Operational Readings

With the calibration complete, test the system under normal operating conditions:

• Turn the Booth On: Start the spray booth fans with clean filters installed.

• Establish Baseline Pressure: Note the new reading on the manometer. For a booth with brand new filters, this baseline static pressure typically reads between 0.15″ and 0.25″ w.c. (refer to your specific booth model’s drawings for the exact baseline pressure).

• Mark Your Limits: Use the adjustable red pointer flags on the manometer casing to mark your baseline (clean filter) start point and your target change-out pressure limit (typically 0.50″ w.c. or as specified by the filter manufacturer).

⚠️ CRITICAL SAFETY NOTE Never use standard water or substitute fluids in the manometer. The gauge is precision-calibrated strictly for use with specific red gauge fluid (0.826 specific gravity). Using any other fluid will result in inaccurate readings, unsafe booth pressures, and premature or delayed filter change-outs.