Best practice for installing a baghouse magnehelic differential pressure gauge

This simple baghouse accessory can mean the difference between a properly functioning baghouse and an operational disaster! Use this guide to ensure proper installation and maintenance of your differential pressure device.

By Dominick DalSanto
Baghouse Technology Expert and Sales Director

One of the most common issues we identify during our dust collection system audits/inspections  is poorly installed and maintained differential pressure system components (e.g. magnehelic/photohelic gauges, DP air lines, DP taps, etc.). As we have covered in previous articles in this series, having accurate differential pressure readings is essential to proper dust collector operation.

Baghouse differential pressure air lines

Avoid the example here. Avoid splitters and crooked lines.

I was recently asked by one of our readers if we could write an article on how to install the differential pressure reading system components for a baghouse. The process, like many baghouse-related items, is not complicated. However, there are some industry best practices that make maintenance easier and reduce likelihood of problems in the future.

This guide can be used regardless of what kind of differential pressure reading system you are going to use. The process is the same for magnehelic and photohelic gauges, as well as timer boards and control boards with on-board pressure sensors.

Installing a Baghouse Differential Pressure System

  1. Determine what kind of differential pressure controls you will use
    • Magnehelic gauges are simple and provide reliable data. However, they alone cannot be used to control the cleaning system on a baghouse.
    • Timer boards are useful for processes that are consistent in dust loading and operating schedules, but must be manually set by operators.
    • Clean on demand systems are the best choice for controlling a dust collector. Often, these systems are all in one controllers, or they are a mix of a control board with an external photohelic or magnehelic gauge for pressure readings
    • Air lines running between the controls and the baghouse can be plastic, carbon fiber, or even metal (copper or aluminum). Plastic or carbon fiber lines are easier to run, but metallic lines are much more durable and will require far less maintenance in the long run.
    • Consider installing secondary magnehelic gauges for redundancy and easy reading by maintenance personnel.
  2. Decide on the location of your control(s)
    • Locate your controls where they can be easily accessed by maintenance personnel. With smaller units often the most convenient location for controls and gauges will be on the ground level. Good locations include on supports or nearby walls. On larger units, controls are best located near the doors or along access platforms. Common locations include next to the door, above the pulse valves and compressed air header, or on a nearby wall or column.
  3. Decide on the location of your air taps and plan your air line runs
    • Air taps are best placed near the corners of the clean and dirty plenums. This minimizes the amount of dust that can enter back into the air lines and possibly foul the DP sensors. Try to keep them about at least 6″ from the walls and in the corners where practical. Keep both taps near each other for easy access when performing maintenance.
    • Decide on the best path for your air lines. Avoid runs over 100′ as this may affect the accuracy of the readings.

Common Issues with Dust Collector Differential Pressure Gauges

Problem: I hooked up the DP lines, but my DP sensor is giving me a negative reading.

Solution: You likely have the lines mixed up. Try switching the lines on the inputs.

Problem: I have the lines set up correctly, but I am getting very low readings (usually under 1″).

Solution: Before installing the both lines, you need to zero out the gauge. Attach one side and then with the other one off zero out the DP sensor. Now when you attach the second line it should give an accurate reading

Problem: My controller is setup, but the solenoids are not firing.

Solution: Check your wiring to make sure you have everything correct. Often, the common line from the solenoid to the control is mixed up with one of the control wires. Double check everything and follow the wiring diagrams from your manufacture exactly. 

Special Thanks

A special thanks goes out to one of our readers, Tim Skiba, for suggesting this subject for an article.  If you have any topics that you would like to see discussed on, please share them with us in your comments below. Thank you so much for reading.


| Dominick DalSanto is an author & dust collection technologies expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as sales director at His articles have been published not only on , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.

17 replies
    • dominickdalsanto
      dominickdalsanto says:

      You should make sure to have a DP gauge (as this article mentions) along with a broken bag detector/opacity meters and thermostat to make sure you don’t have any temperature surges that can damage your bags. It also would be wise to monitor closely the makeup of the gas stream to make sure you don’t have any spikes in acid composition of the gas that could affect the bags or housing (acid flash)

  1. Gireesh
    Gireesh says:


    Is there any filter is required when using a DP sensor? Since it measure the DP between clean air chamber and dusty air chamber


    • dominickdalsanto
      dominickdalsanto says:


      Most gauges do not have filters on them as this would add more resistance to the incoming air and thus throw off the measurements. For this reason, all gauges will get fouled from time to time and need to be replaced. You can help prevent dust from entering into the dirty air line by placing the taps into the dirty air chamber in the top corners of the compartment.

    • dominickdalsanto
      dominickdalsanto says:

      You will need a much more sensitive DP gauge than what is used for baghouse systems. It is possible though.

    • dominickdalsanto
      dominickdalsanto says:

      Usually the cyclone will come with the expected DP loss on the spec sheet from the OEM. There is no point in monitoring it while running because it will always be roughly the same (unless you dramatically raise or lower the airflow).

  2. Bob
    Bob says:

    I am a bit lost on this one:
    “Problem: I have the lines set up correctly, but I am getting very low readings (usually under 1″).

    Solution: Before installing the both lines, you need to zero out the gauge. Attach one side and then with the other one off zero out the DP sensor. Now when you attach the second line it should give an accurate reading”

    If I attach one line, witch should it be?
    And are you meaning to do this while the unit is not running?
    Thank you.

    • dominickdalsanto
      dominickdalsanto says:

      HI Bob,

      you can zero out the gauge with no lines connected to it at first. This will usually fix any problems. Doing it with one of the lines attached is a different procedure.

    • dominickdalsanto
      dominickdalsanto says:

      Hi Louis,

      Are you referring to the reading on the differential pressure gauge? IF so, that measures inches of water, not PSI. A properly functioning baghouse should run usually between 3″ – 6″ depending on the style of the collector…with cartridges or movable arm reverse air units it should be closer to 1″ – 3″. If its outside the range then it indicates a problem.

  3. Nate
    Nate says:

    hello sir, my magnahelic gauge stays at 6-8 when bag house is running but no dust collecting. and 10 or maxed out, when truck is unloading bag house collecting dust. suggestions please. thankyou!

    • dominickdalsanto
      dominickdalsanto says:

      When you first install bags the DP should be around 1″ just from the clean bags. Once they get loaded with dust it should rise above 2″ or 3″ and not really go much lower than that going forward. Your description is not very detailed but it sounds like either you have old bags in it that need to be changed or you have old bags + the baghouse is undersized so that when you start unloading the trucks (i.e. putting a load on the baghouse) the cleaning system cannot keep up with the load and it shoots the DP up to 10+. Also you should make sure the DP gauge is working…you may have to zero it out to ensure its giving you an accurate reading or clean out the airlines or reinstall them to make sure they are working correctly.

      • Nate
        Nate says:

        Thankyou. I know the bags haven’t been changed in at least 10 years. Il change them and do some checking on a few things. Thanks for your help.

  4. Joe OLEARY
    Joe OLEARY says:

    Just finishing a Clear Vue cyclone install. I just want to monitor the change in pressure to the filter stack so I can determine when they’re clogging (about +3 in.) I’m confused on the pressure differential connections to the Magnehelic.
    Do I connect the line from the cyclone to the gauge at the low or high pressure port?
    By my reasoning, it should be the high since the static pressure at the entry to the filters should be higher than the ambient room pressure.
    Is this correct?

    • dominickdalsanto
      dominickdalsanto says:

      Hi Joe,

      We don’t typically install a DP gauge on the cyclone as its a fairly set amount of pressure drop on it (usually the cyclone OEM will give you a rating showing what the pressure drop is at XX CFM and XX CFM.

      For the DP lines on the baghouse you install them one on each side of the tubesheet. Both sides will have vacuum compared to the pressure outside so if you leave one tap off you will see the same effect.


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