Milk Vacuum Pump

The ideal pump has the following parts:


1. The PUMP:


What is most important about this piece is that it is vacuum (sucking air in) and NOT a air compressor (pushing air out).

To the right, in the photo, is a yellowish tube that holds oil. (I use a Vacuum Pump Oil from a dairy store. I have re-filled mine once and have not refilled it in 3 years.) Note, many new pumps are oil-less. There are pros and cons to both styles, but don’t let it bother you too much as a factor when purchasing as long as the exhaust is clear/clean.

Our Surge pump is an old model, nearly indestructible. Pump models vary by design/style considerably. The Gast pump is a modern model commonly used on vacuum pumps for milking machines.


“To put oil in pump unscrew muffler pipe from Tee and pour oil in Tee. When full, oil should show 3/8 inch in transparent hose when pump is not running. If oil does not show in hose, add to get proper level – always keep oil showing when pump is not running.” 1c

2. The MOTOR:


Our pump uses a Dayton 1/2 hp motor, a perfect size for this pump. 1/2 hp is a good “minimum” effective size for most pumps, although larger pumps may do better with 3/4 or 1 hp.2b

Beware: Some of the older pumps have this pulley system. (While it makes for a very smooth working unit, it can be dangerous to fingers, etc.)

The pumps originally came with guards. Ours did not have one when we acquired it, so we keep that side towards the wall.

3. Vacuum GAUGE:

3The gauge is very important!! Improper vacuum causes one of two problems:

  1. Low vacuum = pulsator will not function or pulsator will work but the inflations will not have enough vacuum to draw milk out of the teats.
  2. High vacuum = stresses teat ends and can cause permanent callouses which flare open the end of the teat, exposing the udder to bacteria, therefore higher risk of mastitis.

Ideal vacuum is 13.5 Hg (not PSI!)

The amount can be adjusted for extra long distance between pump and machine (if the hose to the machine is really long, like 50 feet, up the pressure to 14 or as needed to get adequate pressure to pump.)

4. Vacuum PORTS:


  1. The gold colored port on the left is called a vacuum regulator, it regulates the amount of vacuum, and works by simply twisting up or down to adjust.
  2. The port in the middle/bottom is a on/off valve (the handle to switch on/off is out of view underneath). We always leave ours open and leave our air hose attached, but this port may come in handy if your pump is a great distance away. Then, the on/off switch would be where you attach the air hose rather than right up next to the tank like ours is. The other end of the air hose attaches to your milking machine.
  3. The port on the right attaches to the gauge.
  4. The port to the right/rear connects the air tank to the valves.



5aNote: If you DO NOT have an air reserve tank (the large blue tank on the bottom of the setup), your gauge will likely fluctuate significantly.

The needle should not move at all once all four inflations are on the cow’s teats.

If you do have a tank, and you do have issues holding pressure, look at the bottom of the tank and fill in any holes with silicone or something that will help prevent the tank from leaking.

See resources below (from other ingenious sources) for ideas on how to make your own air tank (aka balance tank) for your pump. Click photo for more information.






Using a vehicle as your vacuum pump:


The air tank has an open/close valve (always kept closed, except for cleaning). This valve allows you to clean the tank on the off chance you accidentally suck milk up the lines and all the way back into the tank. Open valve, flush from top end with pressurized air or water, then tip to let drain. The modern Nupulse pump has a large plastic disc on the end of the pump that can be removed, which really makes for easy cleaning!


CaptureThis may seem simple, but for those that do not have electricity in their barn, a plug in can become quite the problem! My dad designed a plug in to the motor that has one line (orange) for the power and another line (black) to a “outdoor” quality on/off switch so all we have to do is flick the switch on and off at the beginning and end of milking.

Be careful to never turn the pump off while the hose is attached to the machine if the machine holds suction. I’ve been told it can make the motor or pump seize. Instead, pull the hose off the machine, then turn off the pump and put the hose away. Return to machine and lift one of the inflations to release vacuum hold in the machine.

Want to know what a milk pump sounds like? Click here to watch a short video:


0machineKeep in mind, the second major part to milking a cow is the machine. CLICK HERE for information on working the machine.



7 thoughts on “Milk Vacuum Pump

  1. Uri d

    Does a fluid catch tank can also act as a balance tank?
    I have a lack of vacuum reserve and also some fluid reach the pump, so I’m considering if adding the catch tank (60 liter) will solve both of the problems.


  2. Joshua M Wagner

    help!!!!!!!!!!!!! how do you flush the vacuum pump out with kerosene if milk has gone through the line into the machine? do you suck the kerosene through the air pump hose and circulate through the machine while leaving the drain open?


    1. They’re probably referring to the air tank – if moisture or milk gets sucked up into that area, it could get wet/stinky. Some are designed to be cleaned out easily, like the Nupulse pump, others aren’t designed to be cleaned very much. My Surge has a small valve at the bottom of the tank that can be opened for cleaning, though I’ve never cleaned it in 10+ years.


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