You need a check valve at the tank as well.
Buy a pressure switch don't rig something. Add a safety valve.

Not a good thing to play with unless you know what you are doing. Compressed air can pack a lot of unwelcome punch.

Last switch I bought cost about $8.
It could be set for cut off and cut on pressures.
I set it to cut on at 80psi and cut off at 100psi.
But I could have set it at other values.
It would handle 110v or 220v current.

You need a pop-off safety valve at 10psi higher than the cut off pressure.
And right after the compressor put a check valve.

My first air compressor used a compressor out of a refridgerator
and a propane tank about 12 inches diameter by 4 feet long.
It was slow but it worked. Friend used a water heater tank for his.
Then I moved up to a commercial refridgeration compressor.
Then finally bought a Sears-Craftsman compressor.

Pooh Bear

thank's poobear..where would I find the item's you mention?
sound's like I did the same set up as your first,it is slow
to build pressure but last a long time,,I currently have a
guage off of an old a/c r12 charge manifold screwed into the
LP tank,and never let it go beyond 100 psi before I manualy
shut it down,and I never leave it unattended,but would simply like to be able to set the cycle myself like 90-100
psi for my air tools and such,it just for household use.
what is the part called? cut off switch,pressure switch?

If you don;t put a check valve in it it will continue to be slow and will not put to capacity. Agter a while it will hit the wall at 65 to 7 psi.
I don't know where to find cheap pressure switches a good Furnas Hubble should be about 40 bucks, safety valve about 15 bucks and check valve about 17 bucks for good stuff.

W. W. Granger has the stuff if you have a friend who can buy it there. Or Sears.

"Friend used a water heater tank for his."

Definitely something I wouldn't recommend!
It may have internal corrosion (sometimes the "glass" lining can have a flaw) and be a potential bomb.

yea,I agree with the water heater comment,not the best of
choices for a tank,but I figure a cast iron 40 gallon L.P
tank should not explode and take out my neighborhood at
125 psi ....OH! SH*T! RUN!!!!! lol....

Waterbird-
You might give your local LP dist. a call and see what pressure they hydrostatically test their tanks at. I think they have to do that every 5 years or so.
Maybe they would test yours for a nominal fee when the do a batch.

Friend had a lawnmower shop.
Never really needed over 60psi.
That's about regular water system pressure.

Looking at a pressure switch from Northern Tool.
In the catalog: item # 16151-1701 $36.99

Also have the Surplus Supply catalog here.
Several are listed in the catalog and go up in price.
Looks like you would want #436-DSV $19.95
If you don't need over 100psi there is one that cuts off at that.
$9.95 item # 11-3042

Probably can find these things at the local big box stores too.

Pooh Bear

If you wanna use a propane tank (and I mean ANY propane tank including the big, heavy ones), be SURE you mount it inverted. That way you can put in a drain valve for the condensation. Drain it FREQUENTLY! A friend built one years ago. Last year it exploded a few seconds after his daughter walked past it. It blew thru a 2 X 12 with enuff force to blow the tire on his truck on the other side of the 2 X 12. He kept his charged to 200 psi, but I'd be careful with anything over about 45 psi just to be safe.
HTH, Don

Dangerous!In my opinion.But I know what a faulty tank can do.My brother had a 25 gallon Sanborn air compressor that was not very old.He used it about every day so he did not take the time to drain it after each use.This was several years ago and it did not have a bottom drain valve.

Luckily he was not in his shop when a faulty weld blew one end of the tank out.It did $800.00 damage to the building as it blew through the wall.He learned to shut his replacement down and releave all pressure and drain the tank after each use with his replacement.

I know a few guys including my father.Who do not realise the danger of a air compressor.They just want to hang on to every dime.They have repaired air compressor tanks that have developed pin holes.There fix it to put JB weld in the pin hole area.Dangerous!Because if there is a pin hole area caused by rust.That tank is thin from rust and you can not see just how bad it is on the inside.Where the rust is.

So dad has about 5 aircompressors he has picked up cheap and thinks he has something.Can not tell the old buzzard nothing.His buddy who is also a junk picker taught him this bad habbit of collecting and using things that were tossed for a good reason.I just bought a new Air Compressor and dad thought I was throwing money around.Because he had one of his jewels he would give me.

I told dad I would rather be alive not killed or in the hospital with metal in my face.Or have to call the insurance company to tell them a JB weld patched aircompressor tore through my garagage and my car that was setting in it at the time.

My point is this.Is it worth trying to build a Air Compressor?There relativley inexpensive and will last for many years with proper care.The main care is to drain the tank.If the drain cog fails replace it.Adding a little never sieze while threading the drain cog in from time to time will prevent it from rusting up.Saftey first.

The drain is a critical component if you want it to last.
I fitted my big stationary type with 1/4 pipe and a lever valve so I do not have to get down on my knees to open it.
Every time I use it, shut off the air line and a quick open/close of the valve blasts all the water out.

"Never really needed over 60psi."

1 SQ.FT = 144 SQ.IN.
60x144=8640 LB./Sq.FT.
That's only a bit over 4 tons/Sq.FT.

well....maybe I stand corrected..think I'll go by one instead....good advise from all.....thank's

You don't need to buy a whole one if you just need a tank.
You can buy just the tank.
Last compressor system I built I bought the air tank
from a big truck junkyard. It was an auxillary tank
from the air brake system. Payed $15 for it.

Surplus Supply catalog has replacement tanks for air compressors.
20 gallon tank item # 4-988 is $129.95
30 gallon tank item # 4-989 is $149.95
Tanks come with wheels and handles and drains.

Just don't use a water heater tank.
The tank may never explode but if your home insurance agent ever
walks in to your shop and sees this redneck contraption he will.

Pooh Bear

ha..sure he would, I was just flippin' through the pages of my northern tool catalog and see the switch(36.99) you're
talking about,but when I add up all the saftey add-ons,switches,valves etc I would be upside down cost wise to
build one..and there's no drain valve on the tank so that's
another issue it would ruin my air tools,but i'll keep it
as is just to blow out things,but I think their's some sage
advise on these forum's,that's why we come here,and the saftey issue is a serious decision to consider when I can
buy a new one for under $200 as opposed to piecing one together..and I likes my innards where they are! but I do appreciate the input....

I wholeheartedly agree with everyones cautions about building your own air compressor but I take exception to what I feel is a little overdone. Draining the moisture from the tank. I agree it should be done and I agree it is something that should be done daily in a large compressor but.... if you are negligent and let your tank become 1/2 full of water then you will only have half a tank of air at the pre-set pressure. It isn't any more apt to explode than if the tank were empty of water. Your symptom will be short cycling. If you think emptying your tank eliminates moisture you are flat wrong.

I just bought this 2hp 25 gallon Sears compressor and its not one of those oiless fish equarium pump type.It was on sale and most of the time is $379.99 sale price.But a few weekends ago they had a deal to good to pass up.20%OFF tool purchases.So I bought this compressor and the HD 50'air hose and some other items and that brought the price up to well over $400.00 I ended up getting the air compressor for $309.and change.

Its super quite and does everything I expected from it and more.It was a online promotion.But I just bought it online and picked it up at my local store.

Here is a link that might be useful: Craftsman 2hp 25 gallon

johndeere you bought a good one. Your description of the oil less compressors is priceless. Aquarium pump.

The reason I built my first compressor 30 years ago
was because we couldn't afford a compressor then.
A fridge compressor was free and I had a propane tank.
Didn't use a cut-off switch for that one. Just added
a guage and a pop-off valve. Kept an eye on the guage.

Last one I built was about 15 years ago. I had to replace
the motor in my F350 dump truck and the motor I got from
a junkyard had an A/C compressor on it. So I got a tank
from a big truck junkyard and mounted it under the bed of
my truck. Plumbed the compressor to it and a guage in the
cab. Put an on/off toggle switch on it and added a pressure
switch to kick the A/C clutch on/off as needed.
Also it had a pop-off valve on it to blow at 125psi.
Worked great for portable air to inflate tires and run small tools.
Sold the truck 5 years ago but I still see it now and then
and the system is still operational. Wish I had kept it now.

Pooh Bear

ingenuity is what makes this country so great!

Don you don't think that moisture cause corrosion that causes tank failure???????

i setup an additional tank for my compressor this weekend. fitted with 2 female couplers and a pressure gauge. i plan on using it when doing lots of work with air tools. my compressor is a small one and just does not have the capacity for extended jobs, so i figure adding the second tank AFTER the regulator gives me more volume of air before the compressor turns on, thus allowing the compressor to cool longer between cycles.

it may turn out to not work as desired for all apllications, but it was free. we had an old tank at work tha twas being thrown out, along with the couplers, tees and the guage. the tank came off a dehydrator, never had moisture in it, so i took it to try my idea.

i tested it yesterday, and it worked fine for the test. my impact usually gets the compressor running after taking off just 2 lug nuts. i took 3 off and put them back on without the compressor kicking in. when it did, it only had to run for an additional 30 seconds to fill the second tank to 90 PSI, so i hope it will work fine.

the tank is rated to 150 PSI, but since it is after the regulator it will never see more than 90 PSI and that is all i felt comfrotable testing it at. i may run a long hose to it and test it higher, but then againg why should i?

there is no drain on it, but there is another plugged outlet that i can remove to drain it. since it will hardly ever be used, this is not an issue.

Granted, anything involving compressed air can be dangerous to begin with, whether it is "certified" or not. Water heater to air tank conversions are out there mainly from a cost perspective and the components are readily available. I have made several over the years for painting cars and houses. I connect them to the regulator of the air compressor. Painting usually involves less than 70psi anyway. There is no substitute for 40-50 gallons of volume at a reasonably constant temperature while painting. If i were to look for an air compressor with anywhere similar volume, it would be over $600. Those of us that have painted cars, etc can attest to the problems that start occurring after a few minutes of spraying: hot air and moisture accumulation. Air dryers start to lose capability when the air temp goes up. Water heaters routinely operate at 90+psi in the house anyway and the pressure relief valve will work with air or water pressure inside. Once you peel off the pretty outer skin and insulation, the steel tank is the same whether it holds water or air. Propane tanks are a thicker gauge of steel because of different regulations covering compressed flammable substances. If i had one available though, i would choose it.

I know this is a somewhat old thread. However here is some advise when building your own air compressor system.

Realize that 2hp is about tops for your motor/compressor unless you want to run on 220V. Even then you'll probably only have a 3hp compressor, so maybe 15 cfm.(see below)
2 hp is equal to roughly 9-10 cfm@ 100 psi, it wont run much, sprayers, maybe a DA for a short time, small hand tools. Don't expect too much.
DO NOT USE propane tanks, hot water tanks, ect. Buy a tank designed for air service, you'll probably save your life.
Do not believe the ratings on the "cheap" compressors you'll see such as Sandborn, IE: 6 hp (notice if the plate on the motor has any "special" ratings and no numbers) and such and such cfm,(usually far too high) it's complete BS.
You will need an air drier, and the only thing that really works is a refrigerated one. If you don't use one your tools will prematurely die(water contamination). The best thing in the world for air tools is clean, dry, air.
You will need an after cooler, most of the ones the tank mounted machines come with are too small.
Put an auto drain on your tank.
This can all be done on a small scale, but still very expensive.(Harbor Freight has DIY parts)
I have designed and installed faily large compressed air systems in the past, anywhere from 15-40 HP to the 100HP 450 CFM IR rotary screw machine we use now.

When I read about what a truck tire blowing out can do, I can imagine what a steel tank would do at a higher voluum and pressure. I certainly would not want to be near that. When my 30year old Sears 20 gal compressor finally was laid to rest (because I needed a part that was no longer available) I replaced it with a Rolair 5520K17. It runs on 120/240 with a 1.5hp motor, and has a 20 gal tank. The psi range is 115 to 135. It is rated at 6.9cfm @ 100psi. Not bad for something that runs great on 120v, even on a 25' extension cord. However, it is heavy (200 lbs), making it difficult to load in my van if I want to take somewhere else. I have to roll it up a ramp for this operation. Charles Ranheim

Good Project! Suggestion after using a Sears 1 HP Electric,10 Gal tank since 1973:

1. Use a good 15 amp timer to cut-off the power incase it fails and runs due to a leak.

2. Add a section of pipe with a valve to collect the condensation and wear vs your tank.

3. Locate it away in a closet etc and plumb to work-bench, garage door, backyard, etc..

4. My Sears' tank developed a leak in 2-3, a self-taping screw and o-ring has held since.
One pin-hole was bad vs entire bottom, I have a new tank that had a bad weld waiting.

Have Safe Fun! loger