Introduction: Convert a Tire Inflator-type Air Compressor Into a Vacuum Pump

Picture of Convert a Tire Inflator-type Air Compressor Into a Vacuum Pump

A vacuum pump is just an air pump, like a compressor, where you use the input side for suction, rather than using the output side for blowing.

Many air compressors make good vacuum pumps if you can find the air intake, enclose it, and attach an appropriate hose or fitting.

In this instructable, I'll show how to convert a 12-volt "tire inflator"-type air compressor into a vacuum pump. This makes a vacuum pump suitable for vacuum bagging laminates and composites (like fiberglass), or for evacuating a tank for a small vacuum former.

The vacuum created is several times stronger than any vacuum cleaner can produce, and most of the way to a perfect vacuum. (About 25 "inches of mercury" out of a possible 29.9, or 12.3 pounds per square inch---or 1768 pounds per square foot.)

It is strong enough to achieve professional-quality results for many processes that require vacuum.

I got my little air compressor for $2 at a Goodwill Blue Hanger store (a.k.a. "Goodwill Outlet Store"). New, it would cost about $20. Converting it to a vacuum pump required a few dollars worth of parts & glue.

In addition to the pump, I used:
a few feet of 1/4" inside diameter braided PVC tubing
a nylon fitting with a hose barb for 1/4" I.D. tubing, and
some J.B. Weld steel-filled epoxy

All of these things are available at home improvement stores.

Since this is a 12-volt device that draws almost 4 amps, it requires a fairly hefty (DC) power supply. I run it off my 6-amp car battery charger. (Or sometimes off of a 12-volt deep cycle, trolling motor-type battery, for vacuum forming in locations where A.C. power isn't available.)

Thanks to Doug Walsh and his book "Do It Yourself Vacuum Forming for the Hobbyist" for the basic idea.

I've done very similar conversions of "nebulizer" air compressors (for medical equipment) from thrift stores. They're quieter, but don't pull as hard a vacuum. (About 17 inches of mercury or 8 pounds per square inch.) That's still several times harder than a vacuum cleaner can suck, and good for vacuum-bagging things like RC model airplane wings, but only a little more than half the ideal vacuum.) The upside is that they're quieter and run cooler, and will likely last longer.

NOTES(added in light of comments below):

If you use a really, really cheap tire inflator, such as the $10 "mini air compressor" from Harbor Freight, don't expect too much. Really dirt cheap inflators may only run for a few minutes before overheating. (Better inflators can run for up to an hour. ) Err on the side of not running your pump for too long at a stretch. If you don't know if it's rated for more than 15 minutes, only run it for 5 or 10 minutes at a time, giving it 5 minutes to cool down before restarting it. Ideally, you'd like a pump with a heavy finned aluminum cylinder, a cooling fan, and a powerful motor, rated for continuous long runs. (Really ideally, you'll get it for $2 at the Blue Hanger.) Failing that, be gentle with your cheap little pump.

Some tips on keeping the workload within your pump's limitations:

For vacuum bagging: (1) don't expect to use this pump for things like full scale airplanes, or to cope with substantial leaks, (2) use a modest-sized vacuum reservoir so that you don't need to run the pump all the time, or for a long time just to build up vacuum in the reservoir. Either use a vacuum switch to top off the vacuum automatically now and then, leaving the pump off most of the time, or do it by hand. If the pump is running most of the time, something is wrong.

For vacuum forming: (1) don't expect to empty a 30-gallon water heater tank with this thing. (I use a 7-gallon $20 Wal-Mart air carry tank for my 12 x 18 inch vacuum formers.) (2) Use a two-stage plumbing system to reduce the load on the vacuum pump and make your small tank go much further. (Like this one, using a vacuum cleaner to suck most of the air out, and an evacuated tank to pull the plastic down hard: .) (3) Don't run the pump until it tops out at 25 inches of mercury or so unless you're forming thick plastic around tight details. 20 inches is plenty for most vacuum forming purposes, and the last few inches take longer, and wear out your pump that much faster.

Step 1: Open the Case

Picture of Open the Case

Figure out how to open the case, and open it. In this case, I had to remove an end cap by pinching it to release a tab, then unscrew a few screws, and I could take the two halves of the case apart. I also had to partly unstick some foam strips across both halves at the bottom.

(The way some cases are put together, you may have to remove rubber feet that are glued over the recesses where the case screws are. Both of my nebulizer pumps were put together that way.)

Inside you'll find an assembly with a little motor, a couple of gears, and a little piston pump. In this picture, the motor is near the center, and the pump cylinder is on the left, with the compressed air hose coming out near the top.

Step 2: Find the Air Intake

Picture of Find the Air Intake

Once the case is open, you can flip the motor/pump assembly up and inspect the cylinder to find the air intake---that is, the holes where the air comes into the cylinder before it's squirted out the compressed air hose.

Some pumps have a hose barb or other fitting connecting to a muffler. If yours does, that's great---you can just use the hose barb that's already there.

This pump just has four little holes in the top of the cylinder. (Actually, there's a little filter under the holes, but we can ignore that.)

Unfortunately, the holes are down in a funny-shaped recess, so we can't just glue a hose barb directly over them. We also want to make sure that the glue doesn't slop into the holes, so we need a couple more steps to make things fit.

Step 3: Find/make an Appropriate Hose Fitting

Picture of Find/make an Appropriate Hose Fitting

I chose to use 1/4" inside diameter braided PVC hose as my vacuum line. It's flexible and stands up very well to vacuum, and you can buy it by the foot in the plumbing department at Lowe's. I bought three or four feet for about a dollar.

To fit the hose, I wanted a hose barb for 1/4" I.D. tubing. There are many fittings (also in the plumbing department) with a hose barb on one end.

I chose a nylon double-ended hose barb (or "butt splice," for connecting two hoses), and cut off the extra barb with a razor knife. That left me with one barb with a flanged base suitable for gluing down, for about a dollar and a minute's work.

Because of the funny shape of the recess on top of the pump cylinder, I also shaved down two opposite sides of the flange, so that it would fit down in the recess. That took another minute.

Step 4: Prepare the Intake for the Vacuum Fitting

Picture of Prepare the Intake for the Vacuum Fitting

To prepare the top of the cylinder for the hose barb, I built a little wall around the intake holes using J.B. Weld high-temperature metal-filled epoxy. (Available at any hardware store for a few dollars; I used less than a dollar's worth.)

First I prepared the surface, swabbing it with alcohol on cotton swabs to remove any dirt and especially oils.

As you can see in the picture, the J.B. Weld was a bit runny at first, and almost flowed over a couple of the holes. Oops. I should have waited until it set up somewhat, to a more putty-like consistency. I pushed it back from the holes with a cotton swab a couple of times. Once it was thick enough to stay where I put it, I shaped it into a circular wall that the hose barb flange could sit on.

Meantime, I mixed up a little more J.B. Weld, so that it would thicken a little, too, in preparation for gluing the hose barb on.

This was the time-consuming part---waiting about hour or so for J.B. Weld to thicken. I had other things to do, though, so I only spent about 20 minutes actually working on this project. If you're in a big hurry, you could probably use faster-setting epoxy, but I like J.B. Weld because it's fairly good at conducting heat. (I didn't want to insulate the top of the cylinder too much. That probably doesn't matter, because a pump used for vacuum doesn't heat up as much as one used for compression---highly compressed air gets very hot---so you might try 30-minute epoxy instead.)

Step 5: Attach the Vacuum Hose Fitting

Picture of Attach the Vacuum Hose Fitting

Once the little wall around the air intake was built and reasonably firm, I glued the the hose barb on, with slightly thickened J.B. Weld. I also put more J.B. Weld around and over the base flange, and let it all set overnight.

Step 6: Attach Vacuum Hose

Picture of Attach Vacuum Hose

Now we attach the vacuum hose by working it over the hose barb, and the motor/pump assembly back where it belongs, more or less.

You don't generally need a hose clamp to hold it tightly to the barb, if your hose is fairly rubbery. (That's one reason I chose the flexible PVC.) Vacuum will tend to suck the hose inward onto the hose barb, making a seal, rather than stretching it outward and making a leak.

Once the hose is in place, you need to figure out how to route it out of the case.

For this pump, there isn't much room to route the hose through the case without kinking the hose or stressing the hose barb, so I chose to just run the vacuum line straight out the top.

Step 7: Make a Hole in the Case for the Vacuum Hose

Picture of Make a Hole in the Case for the Vacuum Hose

I made a hole in the top of the case to run the hose through.

This was easy, since the hole I wanted was at the seam between the halves of the case. I just used nippers to make roughly semicircular holes at each of the mating edges, so that they'd make a roughly round hole when put together.

Step 8: Put the Case Back Together

Picture of Put the Case Back Together

Then I nestled the pump assembly fully in its place, mated the case halves with the hole around the hose, and screwed the halves back together. Then I pushed the end cap back on the end until the retention tabs clicked.

Step 9: Cut Off Tire Inflator End of Compressed Air Hose (for Now), Stow Hose

Picture of Cut Off Tire Inflator End of Compressed Air Hose (for Now), Stow Hose

I didn't want the tire inflator fitting on the compressed air hose restricting the air flow through the pump, so I cut the hose near that end.

(If I ever want to use the pump for inflating tires, I can splice it back together, using the same kind of double-ended barb shown before.)

Then I coiled up the hose and stowed it in the hose-and-cord storage compartment.


Higgs Boson (author)2012-04-07

How high of a vacuum can this create?

batman96 (author)Higgs Boson2012-06-19

I just made one with a 110v compressor that was like the one in the ible, but about twice as big, it went to 29.5 in hg, about 99% of a complete vacuum.

alanjamesblair (author)batman962017-01-13

Is 29hg more than enough for degassing silicone and acrylic epoxies? I assume you get pretty close at 90% full vaccuum, right?

Higgs Boson (author)batman962012-06-21

Wow! That's pretty good for moding a compressor. unfortunately I need a pump which can get down to about 15 - 10 microns. I guess I will just have to buy a 15 micron refrigeration service pump and give it high quality oil to boost performance.

batman96 (author)Higgs Boson2012-06-22

Woa, what do you need 15-10 microns for, that sounds like a awesome and dangerous project, are you making X-rays?

Those things are really expensive.

I got a more accurate measurement based off when water at a certain temp starts to boil in the vacuum, I get more like 29.02, but that is only running it for 10 seconds after the gauge stops, so if I try running it longer it might get lower.

I got a question for you, you seen to know something about vacuum, it seems to me that when my pump is pulling a full vacuum, that would be about the same strain on the motor as if it was pumping 14 psi, or 1 atmosphere right?


Higgs Boson (author)batman962012-06-22

I need high levels of vacuum for constructing electron accelerators, and to tell the truth I haven't actually used a pump yet. I have been researching which is the best to buy, and where to buy it as well as how I should use it. Sorry, I wish I could help you with your question but as of now I don't have experience.

aclark17 (author)Higgs Boson2017-01-02

Well shhh...oot I hope I don't need one that strong just yet, I'm also researching on DIY vacuum pumps to construct electron accelerators lol, Let me know what you come up with!

batman96 (author)Higgs Boson2012-06-22

Does the level need to be that high? From what I understand from my research into vacuum tubes is that it is like trying to shoot a bullet through an ultra dense asteroid field, when there is no vacuum, it isn't going to happen, and with a high but not ultra high vacuum it is like shooting bullets through a super thin asteroid field, most of the bullets will go through and there will be very little loss of electrons.
I hope that makes sense.

I haven't made the pump I put a link to, but he says he got down to 150 microns, you might try building something like that to play around with before purchasing a big expensive one.

All I got to get is a flyback transformer and I'm on my way to making an osciliscope completely from scratch.

Higgs Boson (author)batman962012-06-23

Well you don't need that high of a vacuum to get it to actually start to discharge, but the more air you pull out the more experiments you will be able to do with it. Hertz actually didn't get accurate results from his cathode ray tube experiments because he didn't have a high enough vacuum in his tubes. He was looking for deflection of the electron beam in a presence of an electric field, but was unable to detect it because his vacuum was not deep enough. It took another experiment in a vacuum of 33 microns to see this. A lot more affects can be seen in the CRT if you have a deeper vacuum.

vicvelcro (author)2013-01-14

I modified one of these just a few weeks ago. I drew enough vacuum to boil water. The gauge I tried to measure with was not properly calibrated, so I can't give any exact numbers.

If anyone else gives this a try, I suggest looking for the 'Slime' brand of mini compressor. I bought mine at the store with the smiley face for $10 USD.

jbrown40 (author)2017-10-14

I have a pump similar to this and need a vacuum pump to stabilize wood forknife handles. This will work fine for my purpose. Thanks for the information.Good job.

OmarJ3 (author)2017-01-13

Hi Everyone, sorry if I'm a little off topic. Actually, I'm thinking of using this type of motor to drive an 8mm home movie projector, with the aim being to transfer the films to video by synchronizing the frame speeds. I haven't found anything on the site here relevant to my cause. All I'd like to know is if anyone can tell me what speed this motor roughly runs at. There is a gear reduction of 4.5 to 1. The hack would be to leave the projector drive intact and just "piggy-back" an external drive by a belt or shaft coupling. The DC motor circuit would include a rheostat. So the question is can the rpms be matched without a complicated mechanical setup? BTW, I contacted the motor manufacturer with the printed numbers, and they gave me a non-answer - like it was some military secret.

celtagallego26 (author)2016-09-18

How powerfull is It??

CT5 (author)2014-08-19

Can someone please tell me if I will be able to make and use this vacuum pump to stabilize wooden knife handles? Any answer, any time is MUCH appreciated!!!

Thank you!

dirtbikedude199 (author)CT52015-08-21

If you can find or mix some that takes a few hours longer than the normal cure time it should work. I tried and it only seemed to work with the extra time due to it not fully penetrating into the centet of the wood.

Starlet31 (author)2015-04-05

I don't know why vacuum pumps are so expensive compared to air compressors, but I suppose there's a valid reason why aside from price gouging! Regardless, I need one for lost wax casting (the vacuum pulls the air down and out of an investment mould when using a vacuum table to allow the molten metal to flow deeper into all the detail) and I have an oil-free Clarke air compressor I'd like to use since it has a diaphragm and metal piston. I'm a bit dumb when it comes to stuff like that so I was hoping you might be able to advise me on what I'd need to modify to convert it? I've attached a few pictures of the parts I think are relevant for the modification and a scan of the parts diagram (there's too many to list here, so if you ask about a specific number(s) it would be easier and less space consuming to just tell you what it is).

I've read another tutorial on modifying an air compressor which looks more relevant to mine:

But it's hard to communicate with the author (my last message to him was met with a one line reply and a link to buying a vacuum pump that cost over £160!), so I'd really be thankful for any input here? Thanks in advance!

CrafyStonerDrew (author)2014-07-18

i just wanted to know would this work with concentrates ? enough to pull all butane out of the product? after a heat bath :) please let me know any inforrmation would be grealy appreciated

DanK4 (author)CrafyStonerDrew2014-10-31

I have a 120VAC/60Hz, 1/5HP, 1,750 RPM 30PSI air compressor that plugs into the wall... im wondering if i can convert this for vacuum purging.

fcharest1 (author)2014-03-10

I have one question do we need to keep the one way clapet intact ?

FancifulMatermind (author)2014-03-06

This looks like an excellent Instructable! I do wonder, could you use this for vacuum forming? I was going to need a Shop Vac for the project I'm looking at, but if I could use this, it would be preferable.

RadiantOnyx (author)2014-01-25

Awesome, I'm going to apply the same idea for making a desoldering iron. I could replace the bulb type desoldering iron assembly, add the vacuum tube where the bulb was, have a momentary switch glued to the soldering iron controlling a relay for the pump, and voila!

patrickm (author)2013-11-24

I built one out of a compressor that was identical to this with the only difference being mine had a pressure gauge in the front panel. The best I can get with it is a whopping 18 in. Hg! In fact, that's a lot more than I really thought it would do, but still far from being anything close to what I need. So, I ended up converting an old Harbor Freight pancake compressor I had sitting out in the garage, and I can get 24-25 in. Hg with that. Not sure it that's going to be high enough either, but will give it a try.

I have no idea how the rest of these people are getting anything close to 20 in Hg with these little things, there is no way they are capable of that! That's why people end up spend hundreds of dollars for a real vacuum setup in the end.

Anyway, just my 2 cents.

ajoj (author)2013-03-10


with this pump is it possible to suck the oxygen out of a water tank where the water is 4 inch away from the lid?

batman96 (author)2012-06-19

Thank You!
I have regular 50 gallon air compressor, and somebody gave me a little air compressor like this one, but it is 110v 150 psi, but very well made, it has a 6 inch long motor with a fan at each end, and the cylinder head has fins on it, the intake was in a depression like yours, so I used a right angle hose barb and epoxy putty and installed it, hooked it up to a vacuum gauge and it went all the way down to 29.5 In Hg!
I couldn't believe it almost a complete vacuum!
Thank you for these instructions, I was going to take the thing apart and turn it into a steam engine, because I had no use for it, now I can finish gas discharge tubes that I tried to make with a hand pump, but it just didn't have enough vacuum, it only went down to about 24 In Hg.

mdenunzio (author)2011-09-27

do you think this set up would work to operate a power booster on a car? aftermarket vacuum pumps usually run over 200! i could make this for free today. just mounting is the only issue.

ikes9711 (author)2011-07-22

Will this work with water?

skaar (author)ikes97112011-08-18

till water gets in the pump... perhaps it would be possible to pulse it, pull water into a container, let vac off, pump again. you could use it as a sprayer, air through a constricted tube, a source of water put in at the middle, like a bulb pump perfume sprayer, or carburetor.

skaar (author)2011-03-12

how about... put the entire thing into a box, and seal the out tube... no noodling, and there would be a vac reserve, use a vac switch to switch it on and off...

detchells (author)skaar2011-08-07

The problem with that would be that the pump itself (motor, piston/cylinder, etc) would be operating in a vacuum, so the heat generated couldn't be conducted away by the surrounding air. - It'd almost certainly fry the motor, pump assembly or both in fairly short order.

skaar (author)detchells2011-08-08

unless it went really really really low pressure, i rather doubt there would be a problem with heat conductance. if there's concern, a circulation fan could be put in.

detchells (author)skaar2011-08-09

Good point - I was thinking "vacuum," but these little tire inflators aren't able to pull a very strong one. Still, the author says his unit can reach a vacuum of ~12.3 psi, so that means the pressure inside the box would be only ~14.7-12.3 = 2.4 psi vs normal atmospheric pressure of ~14.7. That's only about 16% of normal, so you can figure only ~~16% of the heat could be carried away vs normal operation. A fan would help some, and the unit might be OK for short runs, but you wouldn't want to leave it running for very long.

skaar (author)detchells2011-08-12 i don't feel very well today, so... ended search here. someone there has a link to a table, but, another says it's irrelevant at low pressures... perhaps low pressure differential is intended, and not important till the differential is large, dunno.

egunawan1 (author)2011-05-31

can I use this kind of vacuum pump to boil a water?

FloydV (author)2009-02-04

Have any of you tried a aspirator vacuum pump. Basically, water sucks the air in as it flows out a pipe. Cheap ($20.00), and high volume and high suction (28.5" Hg). I've used these before and they work really well.

A link for a Nalge pump is:

johnny3h (author)FloydV2011-05-01

Hi Floyd,

I too have used the waterhose aspirator vacuum pump for YEARS for servicing automotive air conditioning systems and it has worked well [down to 28 to 28.5 in Hg], and what I really like about it is that with good, high water pressure, it works FAST!!!!! MUCH faster than "store bought" commercial, OR refrigerator compressors converted. Over the last 45 years I've tried 'em all.

Icetigris (author)johnny3h2011-05-26

Would you be willing to make an instructable on how to use a water aspirator? I want to build a vacuum degasser for resins and a water aspirator vacuum pump seems like the cheapest way to do it.

rick.leasure (author)FloydV2009-02-08

I looked up the link: Product Code NL-LP-6140-0010 List Price $35.95 Sale Price $31.95 Must have raised the price...

troppoforte (author)2010-09-16

Nice little project here!

I love those small pumps with those tiny pistons, the likes of which are in small gas plane engines.

I've actually been pondering turning one of my vacuum pumps into a compressor for an air-powered engine project I have been planning.

I bought three vacuum pumps from my local University surplus warehouse for $5-15 each. One of them is a dual-cylinder pump. It has a direct-drive to the crank as does another of my older ones. My oldest, a Fisher Scientific with a 1/2 HP GE motor, is powered through a belt. That's probably the stongest one I have.

Mattrox (author)2008-10-21

Does anybody know how to change the copressor plug from being car cigerrete lighter powered to mains or run it off a car battery Pleaz Coment

miiwii3 (author)Mattrox2009-08-02

easy buy a 12 volt wall wart you know 120v to 12v and splice the wires together white or dashed wire to white or dashed wire black to black. i believe black is ground or negative ohh and your wall wart must be dc voltage

kikiclint (author)miiwii32010-09-01

air compressors use more power than a wall wort can usually supply, and will either burn up your wall wort, not supply enough power to run the compressor or both. A computer power supply does work ok though. In general, they probably run around 8-10 amps for the model shown in this instructable.

Mattrox (author)miiwii32009-08-02


miiwii3 (author)Mattrox2009-08-02

no problem

rada194 (author)Mattrox2009-08-09

a really easy way is to hook it up to a 12.0 volt drill battery thats what i did and its rechargeable and portable its great

bomihdar (author)2010-08-27

thank you

noledude44 (author)2010-08-23

Would be strong enough to use with a vacuum bag? I'm going to be making a longboard and i'm just checking out different ways to do it.

geoslim13 (author)noledude442010-08-26

there is an instructable on making a vacuum seeler

corbin569 (author)2010-07-21

does anyone know if this would pull a big enough vaccum for a fusor reactor/fansworth reactor... i,m only wanting to make the plasma not introduce a new gas and make actual fusion

e-tek (author)2010-02-07

This is WAY after your postings - but I'll ask anyway. can this be used for a fresh-air system for painting and such? If it sucks air in one tube and exhausts it our the other, couldn't I attach a hose to a mask? Maybe using a nebulizer would make it even "cleaner" and able to run for hours at a time. Plus you don't need much air to fill amask for breathing. Thanks!

votecoffee (author)e-tek2010-02-07

I would avoid using it for that.  Such pumps are designed for higher pressures and running them at low pressures would wear it out quickly.  Also, the air from these isn't as clean as other cheaper options for what you want.  If you smell the air from a tire air compressor it will have a definite odor.  Your best bet is to make a box to enclose a small fan for simple low pressure circulation.  You can get hose fittings for any size hose you want from a hardware store.  I would use a larger hose so air flows easier.  You may not need much air to live, but high levels of CO2 from old air is bad for you as well.

About This Instructable




Bio: I'm a research scientist who likes to design and build things, especially cheap, elegant tools for building things you wouldn't have thought you ... More »
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