Is a 20 gallon compressor enough for air impacts?

[GX460DIYguy]

I’ve been wanting a cordless impact for a while now, but with the initial cost I’ve just stuck to hand tools for most stuff. We’ve got a 20 gallon(could be a 30 gallon) air compressor in the shop and I’m wondering if that’s going to be enough air for most diy jobs without the compressor running non stop? Air tools tend to be a lot cheaper on the secondhand market and I think most stuff we do isn’t going to be anything like an actual repair shop so it’s not like we’re going to be using them non stop all day.

 

[DemoFly]

Yes. Plenty. Set the regulator to 90psi working pressure (meaning 90psi with the tool actually in use) and it will be fine.

 

[finn]

You really need to look at pump delivery (cfm), rather than tank size. Tank size is just reserve capacity, and cfm is what the pump can deliver. Compare delivery vs consumption if the tool you are using.

i survived for years with a 2 hp 240 v Sears belt driven compressor. It worked well with an air impact, and would supply enough air to paint body panels, but there was a lot of waiting to paint an entire car.

didn’t do great with DA sanders.

 

[john.k]

I use a 3/4 drive IR rattle gun to take tyres off tractors with a small Chinese compressor .....about 10cfm max..........you need a big,unrestricted hose from tank to rattle gun ,and you get the few seconds needed to undo big nuts before pressure drops .

 

[u2slow]

Impacts are usually not a problem. Grinding/sanding tools, painting, and sandblasting eat a lot of air.

I have been running a 240v/10cfm/20gal compressor in my shop (mainly impact gun and air nozzle) for almost 25 years.

 

[GeoBruin]

You really need to look at pump delivery (cfm), rather than tank size. Tank size is just reserve capacity, and cfm is what the pump can deliver. Compare delivery vs consumption if the tool you are using.

i survived for years with a 2 hp 240 v Sears belt driven compressor. It worked well with an air impact, and would supply enough air to paint body panels, but there was a lot of waiting to paint an entire car.

didn’t do great with DA sanders.

This is good advice for constant run tools like blast cabinets, paint guns, sanders and the like, but it really is the opposite for "burst" type tools like impacts and air hammers. The Instantaneous air consumption is going to be much higher than the pump can deliver in any case (let's say 40 CFM) so while it may buy you a little extra time if your pump can deliver 20 vs 10 CFM to the receiver, the real usable runtime is going to be mostly dependant on how much initial air volume you have in the tank, which will dictate how long you can ugga dugga before the pressure to the tool drops below the regulated pressure.

 

[908Jim]

I agree with @GeoBruin and others above, but I will add one caveat. Most portable compressors have a 1/4 outlet for the air hose, which creates an upstream restriction. Per this old thread, Milton says a standard 1/4 Type M has a 22 CFM flow rate with 5psi Pressure drop. https://www.garagejournal.com/forum/threads/cfm-through-quick-connects.116630/ 22CFM is going to choke a lot of impacts at load. These compressors often have cheap 1/4 NPT regulators that might not be up to the task.

Make sure you give thought to the connection for best performance. I would swap with coupler with a Milton hi-flow or a 1/4 NPT 3/8 Body coupler, at a minimum and make sure you're using a short 3/8 hose. Don't forget to compensate for pressure drop.

 

[GeoBruin]

I agree with @GeoBruin and others above, but I will add one caveat. Most portable compressors have a 1/4 outlet for the air hose, which creates an upstream restriction. Per this old thread, Milton says a standard 1/4 Type M has a 22 CFM flow rate with 5psi Pressure drop. https://www.garagejournal.com/forum/threads/cfm-through-quick-connects.116630/ 22CFM is going to choke a lot of impacts at load. These compressors often have cheap 1/4 NPT regulators that might not be up to the task.

Make sure you give thought to the connection for best performance. I would swap with coupler with a Milton hi-flow or a 1/4 NPT 3/8 Body coupler, at a minimum and make sure you're using a short 3/8 hose. Don't forget to compensate for pressure drop.

The hose diameter/length are certainly a concern, but I wouldn't worry too much about the connection at the compressor, or even the quick disconnect fittings assuming those are the only fittings in the system. Regarding that 22cfm number, that's not the "rated" cfm for the fitting, it's just rated at a 5 psi pressure drop at 22cfm. You can flow a whole lot more than that through an M style fitting, the pressure drop just begins to increase beyond that, but not so much you cant compensate for it pretty easily with the regulator (here's a quick video I made showing a 1/4" fitting flowing 100 cfm, and that's at the end of a 50', 3/8" hose reel).

Here's a video I made comparing the flow rates or various 1/4" industrial plugs with a very standard universal QD coupler. You'll see I have the system arbitrarily choked off at about 30cfm at 100 PSI static pressure and there's almost no discernable difference in flow between the fittings.

Regarding pressure drop, here's a whole series of videos I made in response to some questions from another user here about the difference in pressure drop resulting from various combinations of couplers and plugs. This series was limited to 20cfm, but in that range, the pressure drop across all samples was well within the ability to compensate on the regulator for most compressors.

 

[Old Man Roger]

I’ve been wanting a cordless impact for a while now, but with the initial cost I’ve just stuck to hand tools for most stuff. We’ve got a 20 gallon(could be a 30 gallon) air compressor in the shop and I’m wondering if that’s going to be enough air for most diy jobs without the compressor running non stop? Air tools tend to be a lot cheaper on the secondhand market and I think most stuff we do isn’t going to be anything like an actual repair shop so it’s not like we’re going to be using them non stop all day.

Not enough to take four 6 lug truck wheels off without letting the tank air back up, but plenty enough to take one or two off. It doesn't take long for the tank to fill back though, so in most cases, a 30 gallon will do the job.

 

[johninct]

Get rid of any regulator, obstructions and use hi flow couplers. Also, you need to get an air impact, such as an IR 231 that doesn't require as much air.

 

[cannuck]

flow only becomes a concern with a few very high consumption tools (1" air impacts, for instance). My 135CFM diesel portable will sandblast all day long on a 1" hose with Chicago fittings even smaller for the air path and no tank at all. Conversely if you actually HAVE really big air demands at a distance things should start large and unrestricted (my 600 gal. tank comes out at 3" NPT)

 

[Jswain]

Just don't use restrictive fittings/hose/preferably regulator and you will be fine.

It DOES make a difference if you use restrictive fittings because you are under gunned on storage so you want your impact working as efficiently as possibly. If you give it 90+psi(at the tool, with the tool running) it will remove bolts/lugs much faster then if you set the regulator to 90psi at the compressor, use a long *** hose, with a low flow fitting.

This matters because if you are under gunned on storage/pump then if the gun doesn't remove the fastener pretty efficiently you'll be waiting.(And waiting, and waiting, and if the fastener is actually tight you may just not have the HP to remove it because you're not feeding the gun enough)

Feed it properly with a 3/8" air hose, preferably no longer than 25ft, and v-style high flow fittings. If you can, run your hose with a shut off valve right off the tank(if tank pressure is 125psi or less) and don't regulate it back at all. If the compressor has a decent regulator on it you can run it right from there, but most of them are more well suited for air nailers etc.

If you're looking for a second hand gun stick with IR

 

[VolvoRyan]

I've found that IR guns do "more" with less scfm than some other brands. Of course, this may be outdated thinking.

It is worth having air tools. My IR 2135 weighs a fraction of the M18 cordless.

-Ryan

 

[u2slow]

I agree on sizable hose and fittings to feed a gutsy impact... but for me it's 50' of 1/2" with at least V fittings. I also tapped the supply with 1/2" NPT because the factory connection is only 1/4" NPT through the pressure switch.

 

[mikedodge]

The compressor will be fine with it but it might start running or need to play catch up while you're using it.

Have you thought of a plug in electric impact? They're pretty cheap on sale like cheap air tool $$ range and I use mine far more then an air impact.

 

[inline five]

I have a Craftsman 25 gal 150 psi compressor and an older Harbor Freight Earthquake impact. I can fill the tank, and take all 20 lug nuts off my vehicle without having to run the tank again (it drops below its start up PSI, but there is enough left to remove all my lugs).

I've done lots of suspension work with it, taken off subframe bolts, crank bolts, and axle nuts again all without issue.

You're not going to run a DA constantly nor paint for 10 minutes at a time but it will do a lot.

 

[zendriver]

I must live on a different planet, whereas my 26 gal compressor is slightly worse than useless, with air impact tools. About 10-15 seconds and it needs to rebuild pressure.

OP mentioned not being able to afford cordless tools. Shazam, Get this deal 20V brushless 1/2' impact and charger/battery for the price of a trip to Appleby's (with drinks).

https://www.harborfreight.com/promotions/bauer-buy-starter-kit-get-free-tool/20v-brushless-cordless-12-in-3-speed-impact-wrench-tool-only-58637.html

 

[sparky 1971]

Will it run an air impact? Yep. Will it run an air impact well? Nope. It will do a better job in Texas than in the snow/rust belt though due to less hammering to break fasteners free. I managed to make it about 18 years using a 30 gallon compressor from Sears before upgrading to a 60 gallon. I agree with losing the regulator, I did that and it really woke the compressor up, I don't run a regulator on the 60 gallon either.

 

[The Cobbler]

My IR 2135 weighs a fraction of the M18 cordless.

 

[Nutria]

Great, now I have an ear worm. You can have it too:

Pressure Drop, Toots and the Maytals:

 

[VolvoRyan]

I must live on a different planet, whereas my 26 gal compressor is slightly worse than useless, with air impact tools. About 10-15 seconds and it needs to rebuild pressure.

OP mentioned not being able to afford cordless tools. Shazam, Get this deal 20V brushless 1/2' impact and charger/battery for the price of a trip to Appleby's (with drinks).

https://www.harborfreight.com/promotions/bauer-buy-starter-kit-get-free-tool/20v-brushless-cordless-12-in-3-speed-impact-wrench-tool-only-58637.html

You may have leaks..... a switch with a bad high/low set point.... or just a worn out motor/pump/valve/stuff. Lots of things to check out when compressors get miles on them. My old Craftsman compressor just needed everything replaced on it. I should have replaced it sooner. I have a spiffy CH two stage now.... but the low pressure triggers at like 150psi on a 175psi compressor. The thing is constantly refilling itself.... without really needing to.

That Bauer impact: I got one. It is fantastic for rebuilding mower decks and fixing other landscaping things. I'm happy as a clam with the purchase. I also got the cheapest SAE impact sockets HF sells. Great. On the other hand, you absolutely get what you pay for with this impact wrench. Probably less than what you pay for. It's a really so-so tool. On the plus side, it won't make you sick like Applebees will.

-Ryan

 

[zendriver]

You may have leaks..... a switch with a bad high/low set point.... or just a worn out motor/pump/valve/stuff. Lots of things to check out when compressors get miles on them. My old Craftsman compressor just needed everything replaced on it. I should have replaced it sooner. I have a spiffy CH two stage now.... but the low pressure triggers at like 150psi on a 175psi compressor. The thing is constantly refilling itself.... without really needing to.

It probably has 20 hours on it.

Wonder why commercial garages waste money on big air compressors?

 

[Jswain]

I must live on a different planet, whereas my 26 gal compressor is slightly worse than useless, with air impact tools. About 10-15 seconds and it needs to rebuild pressure.

OP mentioned not being able to afford cordless tools. Shazam, Get this deal 20V brushless 1/2' impact and charger/battery for the price of a trip to Appleby's (with drinks).

https://www.harborfreight.com/promotions/bauer-buy-starter-kit-get-free-tool/20v-brushless-cordless-12-in-3-speed-impact-wrench-tool-only-58637.html

Any pictures of your setup? Right from the tank to the impact?

 

[john.k]

I once bought a crate of near new 1'' air impacts that were tagged 'wont work / no good' at an auction .....they were fitted with 3/8 Nitto couplings .......I fitted 1/2'' claw type hose couplings and 1/2 hose and they worked properly............the big clue was they had 1/2 NPT inlet thread ,and who ever set them up had bushed down the 1/2 to 3/8 to fit the quick release fittings

 

[zendriver]

Any pictures of your setup? Right from the tank to the impact?

Not at the moment, but it does just have a hose to the tool.

It's a "Speedway" maybe it's not up to the specs it claims.

Just seem odd to me, swear I've heard a million complaints here, about compressor tanks that are too small to adequately run impact tools.

 

[Old Man Roger]

A couple of you have mentioned getting rid of the regulator? Wouldn’t just cranking it wide open work? On a rare occasion I’ve turned it down, not often, but it’s a nice option to have.

 

[Jswain]

A couple of you have mentioned getting rid of the regulator? Wouldn’t just cranking it wide open work? On a rare occasion I’ve turned it down, not often, but it’s a nice option to have.

Not if it has a small orifice. Any decent sized compressor has a bung/elbow/outlet valve straight to your hose/wall. If you choose to regulate then get a minimum 3/8" regulator for running auto type tools, and set it for 125psi if you're running a 50ft 3/8" hose reel...........

Anyone having problems with air tools with lack of power is usually doing it wrong.

 

[Jswain]

Not at the moment, but it does just have a hose to the tool.

It's a "Speedway" maybe it's not up to the specs it claims.

Just seem odd to me, swear I've heard a million complaints here, about compressor tanks that are too small to adequately run impact tools.

Does the hose come straight from the tank, or from a built in regulator?

Once you drain your tank below say cut in pressure on a single stage air compressor you are entirely at your pumps mercy...but if you're draining your tank quicker because your impact is not performing like it should, and every nut takes 15 seconds instead of 1, then there are ways to easily to fix that.

 

[john.k]

A regulator is a major flow restriction ........this is the first thing to eliminate if you want maximum flow with minimum pressure drop.............run the tool direct with a ball valve as shutoff at the tank...........right angle pipe fittings also cause as much loss as a long run of pipe.

 

[Death Row Dave]

Single stage compression is usually 120 psi at most . Use an unregulated tank tap for the rattle gun . Regulated tap for most other stuff and it will decently run the gun.

 

[Old Man Roger]

Not if it has a small orifice. Any decent sized compressor has a bung/elbow/outlet valve straight to your hose/wall. If you choose to regulate then get a minimum 3/8" regulator for running auto type tools, and set it for 125psi if you're running a 50ft 3/8" hose reel...........

Anyone having problems with air tools with lack of power is usually doing it wrong.

Never had any real issues with mine, but now you guys have me curious to see if it would be better without the regulator. I mostly run my 1/2 inch drive and 3/8 drive IR impacts, and a 3/8 Mac ratchet.
My air die grinder doesn’t get much use since I have an electric one, but maybe it would without the regulator?

 

[Jswain]

Never had any real issues with mine, but now you guys have me curious to see if it would be better without the regulator. I mostly run my 1/2 inch drive and 3/8 drive IR impacts, and a 3/8 Mac ratchet.
My air die grinder doesn’t get much use since I have an electric one, but maybe it would without the regulator?

Drain the tank, throw a fitting on the side of the tank(if it has a bung) and try it with a hose.

IR guns love extra pressure...

It might not make a big difference for the air ratchet, maybe the 3/8" gun. But I bet the 1/2" will like it...

 

[mikedodge]

It probably has 20 hours on it.

Wonder why commercial garages waste money on big air compressors?

Because they usually have multiple people and equipment using air at the same time.

 

[zendriver]

Because they usually have multiple people and equipment using air at the same time.

Either that or they don't want to remove 4 lug nuts and stop and wait for the compressor to recover.

 

[Citation]

OP, I think the answer will depend in part on what wrench and what jobs. For a while I was using a 4 gallon roofing compressor (Emglo), a 3/8" hose and an IR 231 wrench with no issues. Most of the time I was pulling 19mm lug nuts off smaller cars. I used it to pull an axle nut once. I think the pump restarted about the time the nut had started to really turn freely. When doing my wheels I think the compressor needed to recycle once or twice before removing all the wheels. The best plan was to make sure that cycling started right as you finished pulling the lug nuts off a given wheel. The pump would recycle while I physically removed the wheel and move to the next corner of the car.

My 26 gallon tank seems to have no issues with pulling all the wheels off one of our cars. However, those aren't heavy duty trucks. Personally I don't see an issue with a 20 gallon tank so long as you have a free flowing regulator and you understand that the pump may cycle before the job is done.

 

[Old Man Roger]

Because they usually have multiple people and equipment using air at the same time.

Or you have a job that requires you to remove 20 or 30 bolts in a row, or you have a bead blaster, or you want to use a die grinder, or you need to air up 4 tires in a row, or you have a tire machine or you…. Well you get it.

 

[DemoFly]

I must live on a different planet, whereas my 26 gal compressor is slightly worse than useless, with air impact tools. About 10-15 seconds and it needs to rebuild pressure.

You just described air compressors.

 

[zendriver]

You just described air compressors.

When I watch my tire shop using one, they don't have to stop and wait for the compressor to recover proper air.

 

[DemoFly]

When I watch my tire shop using one, they don't have to stop and wait for the compressor to recover proper air.

Excellent observation. Neither you or the OP are a tire shop, though. I can run a 1/2" cornwell impact all day long on a 5scfm 8 gallon compressor. If you have to wait for a 26 gallon to catch up, you have a leaking air motor or a worn compressor.

 

[john.k]

I had all my collection of air tools at the last job ......unlimited air at 125psi ........air chain saw ,big IR air circular saw ,assorted Atlas Copco grinders ,straight and disc,air hammers ,even a 90lb IR breaker that was unused when I bought it...........not to mention all my collection of big rattle guns .........big air tools in new or as new condition sell for near zero dollars at auction because no one has the air to run them ...........when I quit at short notice ,they discovered to buy air tools like mine would cost a fortune.