A vacuum pump is basically an air compressor that runs backward. Instead of forcing air into an enclosed container, the vacuum pump sucks and pulls air or other gases out of an enclosed container. The better and stronger the pump, the more air it can pull out, and the lower the resulting gas pressure will be in the container.

Vacuum pumps are versatile tools that, while intimidating, are fairly simple to use. After you’ve used one successfully a time or two, you will likely be confident in using this handy tool. Vacuum pumps may be used for repairing AC units, preserving food, and a number of other uses.

Of course, you do have to get the right vacuum pump for your needs. Are you a weekend warrior who only needs a pump now and then, or do you work with vacuum pumps day in and day out?

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Pumping air or gas out of an enclosed container is known as “pulling the vacuum.”
Required vacuum
Vacuums, whether they are in engines, machines, or enclosed containers of any kind, are measured in microns. A micron is 0.001 millimeters. Air pressure is normally measured in the number of column inches of air. Microns are much smaller, so an air pressure of 40 microns would equal an air pressure of 0.0015748 pounds per square inch.

That doesn’t sound like much — and it isn’t. The lowest air pressure the human body can withstand before the blood begins to boil is 0.89 pounds per square inch. Forty microns of vacuum, in many cases, is the high end of the vacuum a vacuum pump can create. Many pumps can lower that number even more. Modern appliances have requirements for a near-absolute vacuum during the repair and recharge process, so you need to know how much vacuum will be required for the systems you’ll be working on.

Anticipated usage
You should consider how much you’ll be using the vacuum pump. If you’re only using it once or twice a year, almost any model will satisfy your needs. If you need a vacuum pump daily at work, you’re going to need a very robust model that can be easily carried from one location to another.

If you’re using it for vacuum storage of non-perishable items such as blankets and clothes, or if you need to vacuum-pack food for long-term storage, a diaphragm pump would be suitable for you.

For working with any kind of refrigerant, a diaphragm pump won’t be appropriate. You’ll need a rotary vane pump.

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For most AC systems, it is best to run your vacuum pump until the pressure is down to 1,000 microns or, if possible, down to 500 microns.
The nature of the work being done by vacuum pumps requires an all-metal construction, except for the base, which is generally made of ABS plastic with rubberized feet. Aluminum is the most common metal used in vacuum pumps for its low price, although some heavier models use steel.

The more horsepower the engine has, the stronger the pull it will have in drawing gases out of an enclosed container or system. Smaller horsepower engines can achieve the same results as larger horsepower engines over a longer period of time. If you’re not in a hurry, save yourself some money by choosing a pump with 1/4- to 1/2-horsepower engine. If you need more power to get the job done quicker, you should look at a 1 horsepower motor.

Most vacuum pumps have a carrying handle for portability, but some are intended to be installed and left in place. You should have a good idea of which design is right for your needs before you spend any money.

Directly related to portability is the weight. Because of their all-metal construction, vacuum pumps tend to be heavy even though many are made from aluminum. A lightweight pump would weigh in at around 11 pounds, while heavier ones may reach 35 pounds.

Diaphragm vs. rotary vane
There are some crucial differences between diaphragm and rotary vane pumps you should be aware of before you make your selection.


A diaphragm pump has a rod connecting a flexible diaphragm to a rotor. As the engine turns, it turns the rotor which moves the connecting rod up and down, moving the diaphragm with it. As the diaphragm is pulled down, it sucks gases in through the intake. When the rotor moves to the opposite side of the cycle, the rod begins pushing up. A check valve in the intake closes and the check valve in the exhaust opens to allow the gases to be expelled.

Diaphragm pumps don’t require oil, so the maintenance needs are low. Because diaphragms are made of a flexible material, they aren’t suitable for acidic or solvent vapors. Depending on how much a diaphragm pump is used, the diaphragm may have to be changed on an annual basis. Finally, diaphragm vacuum pumps can’t achieve the same micron levels as rotary vane pumps. Generally speaking, however, they are less expensive.

Rotary vane

A rotary vane pump uses a vane that sweeps the sides of a cylinder to pull gases in through intake then expels them through the exhaust. Due to the construction of the rotor and vanes, check valves aren’t required. However, special oils with low vapor pressures are required for lubrication of the vanes and cylinder walls.

The normal operation of rotary vane pumps uses the oil at a steady pace because each time the vanes sweep past the exhaust port, some of the oil is expelled along with the gases. It’s a function of the way the pump operates and cannot be avoided. In order for the pump to operate, you’ll need to keep an eye on the oil levels and constantly refill it. Rotary vane pumps can produce excellent micron numbers but at a greater cost than diaphragm pumps.

Single-stage or dual-stage
A single-stage vacuum pump has less complicated controls and only one set of vanes. The faster the motor runs, the greater the suction. A dual-stage pump has more complicated controls because it has two sets of vanes that give you the option of volume versus pressure.

People assume that a dual-stage pump must be better than a single-stage one, but in truth, the differences are minimal. Both types can achieve the same vacuum, although the time required may be slightly longer for a single-stage pump. Maintenance and oil requirements, however, are the same.

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After reaching your target, turn the pump off and leave it attached for about 15 minutes to ensure the vacuum holds and there are no leaks.
Inexpensive: For under $100 you can find diaphragm or single-stage rotary vane pumps. Some low-quality double-stage rotary vane pumps may be available for this price as well.

Mid-range: The majority of vacuum pumps cost between $100 to $300 and may be single- or double-stage rotary vane pumps.

Expensive: Over $300 is the high price range for vacuum pumps. These are generally steel or all-metal high CFM pumps that are almost exclusively double-stage rotary vane pumps.

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When using a vacuum pump to store blankets, towels, comforters, and other items, only use a plastic bag designed to withstand the force of a vacuum as other bags will not hold a reliable seal.
The oil in a vacuum pump should be changed about every 300 hours.
Never run a vacuum pump unless it has the proper amount of oil in it.
When repairing an AC unit, attach your pressure gauges to the ports on the AC system and your pump before starting it.
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The back end of vacuum pumps is where the heat exhaust is located, so don’t cover it or obstruct it in any way, or the pump will overheat.