View Full Version : Looking to purchase compressor

11-26-2006, 12:42 AM
Im looking at purchasing an air compressor. I originally was just going to spend 500.00 on an eletric one for the garage, but i do a handful of blowouts and i was thinking maybe it would be nice to have a gas unit. Any body have any recomendations. Strictly Residential properties. Anything special to look for when buying a unit.

11-26-2006, 08:32 AM
You might check with what Grainger has. See if you can compare the build of their own house brands, like Speedaire, Dayton, Westward, etc. with Ingersoll Rand. Starting from scratch, with 20/20 hindsight, I'd have spent the bucks (now close to $2000) for an IR on a 30 gallon tank. But you can start smaller, with a 20 gallon portable, with a single-stage air pump, and it can handle your standard residentials, one zone at a time, with a wait between zones, maybe.

It might make more sense to look for a used compressor on eBay. No doubt the money for a new IR truck-mount compressor would go a long way towards a decent used tow-behind.

11-26-2006, 07:55 PM
is gas definetly the way to go, or would it be good to purchase a big electric and a generator. Im not really sure, i normally just sub these out, but its go to the point, where i could pay for a machine in one season on my own. Im looking for something i could either mount on my trailer or load into the back of my truck when i need it. Im sure a complete unit on its own trailer would be quite spendy.

11-27-2006, 10:47 AM
Does anyone use the combination of an electric compressor and a generator? I expect there are limits to what size of motor can be reliably started from a generator. Bolting a portable compressor to a truck bed might put a strain on the pieces of metal that support the tank. Not so much where the wheels are, but the other end, where I've twice had breakage. The first time cost me the tank itself (original non-ASME tank)

Grainger's cheapest (http://www.grainger.com/Grainger/wwg/productIndex.shtml?originalValue=compressor+westward&L2=Gas-Powered&operator=prodIndexRefinementSearch&L1=Air+Compressors%2C) might work well for you. I winterized a football field with one like it, back in the early days. (It had a mainline to inflate, and yes, I brought a lunch) ~ I do wonder about the quality of the build, over a very long term, compared to an Ingersoll Rand. From experience, I'd be looking for a solid heavy platform for the components. I have no gripe about the Grainger pump itself, but I know that the motor platform on my replacement tank was made for electric motors, and not gasoline engines, since it has a tendency to crack once every season or so. (They now list a separate replacement tank for engine-driven compressors - too late for me, though, so I get to play with the arc welder)

If you found a decent used electric compressor, it might be possible to replace the electric motor with a gasoline engine. The usual factor for replacement is 2 - that is, replace a 10HP electric motor with a 20 HP gasoline engine, in order to have the necessary torque to run the pump. If you like to tinker, you might enjoy trying to build your own custom rig, like my current idea of a sled-mounted engine and pump, with a tank on the side.

11-27-2006, 10:53 AM
Try northern tool sometimes you get a good price and free shipping.

11-27-2006, 04:11 PM
Dont waste time or money on a electric rig . Go to the auction and pick up a tow behind . I have bought them as low as 600 dollars that last me 3 years . My 125 cfm diesel was 1100 dollars with 775 hours on it

11-27-2006, 05:30 PM
If you do have the room for a tow-behind, that's obviously the first choice. I'll always keep a truckmount around, so I can get to some of the trailer-unfriendly locations I service. Every part of the country won't have the same access to good older compressors, so it's one of those 'your mileage may vary' situations. I would budget higher for something you could count on a decade of service from. The one advantage of going with a well-known truckmount, is the ability to keep the thing in service, even when you have to replace belts or engines or pumps. (Avoid something you need to trot out the arc welder for, though)

My old Grainger has become something of a 'great grandaddy's axe' with it working with it's fifth engine, second tank, second pump, etc.

11-30-2006, 01:32 PM
i dont want a tow behind rig, id like to just mount a compressor on my trailer, in my truck, finish mowing my property or whatever, and then blow out the lines, i also dont have space for another trailer. What is the minumum CFM i should buy and at what PSI, i was looking at a 50 gallon electric and a compressor, probably around a grand, would this be a bad idea. If not what should i look for in a gas unit as far as tank size and motor horsepower.

Ground Master
11-30-2006, 03:11 PM
$1000. might get you a 8hp gas unit putting out 16 to 20 cfm, but you'll soon realize its a little weak for blowing out systems. Although it can do it, just slowly.

You'd be happier with a 13 to 15hp rig capable of 25 to 30 cfm. New will set you back $2000.

I've seen some portable 25 hp rotary screws that put out 90 cfm. These will set you back $6000. You could mount these units on a trailer.

As far as $ per cfm goes the cheapest route is a used tow behind unit.

Your idea of an electric unit powered by a gas compressor takes up alot of space and will cost alot to get even a minimum of 20 cfm.

11-30-2006, 03:43 PM
The compressor pictured below, is older than you are, and is identical to the one I did a football field with. Probably delivered less than 10 cfm as it was configured. They don't make them that small anymore. With an 11 or 12 gallon tank, the use of a hundred-odd feet of 3/4" hose on a cart made a real difference in the 'air charge' you could build up.

How handy are you? Mechanically inclined? Good at welding? None of the above? That would figure into any idea of buying any old equipment, or the components to configure a homemade truckmount. One thousand is an awkward amount to spend on a new truck-mount, since the going rate for a brand-new solid rig on a 30 gallon stationary tank is closer to two thousand (http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611627230).

This one (http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1613551624) is a configuration they didn't have, back when. Bigger tank, stronger platform, but not as strong as on a stationary built for the larger engines and two-stage pumps. Their current entry-level portable (http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611627244) could be a problem as a truck-mount, since just bolting it to a trailer or truck bed would strain the tank support strap. (construct a wooden cradle to support the tank, to take some of the load off) Another misgiving is the engine platform, which looks a lot like the one that often cracks on my replacement tank.

There are reciprocating pumps that are much more heavily constructed than anything in the Grainger house brands. Ingersoll Rand T-series, for a start. Quincy, for sure. There are others. eBay has them listed all the time, but for something used, that won't be demonstrated as running, your mileage will vary, of course.

Ground Master
11-30-2006, 04:17 PM
ahhhhhhh..........an old speedaire compressor. I have a very similiar unit when I started blowing out systems in 1988. It was ok at best on small systems.

I tried using it on larger systems that had mainlines larger than 1" and it was substandard. Ok, it was actually lousy. Mine was 20 gallons with 100' of 3/4" hose. It would take at least 5 minutes plus to do 1 zone.

I've used several since and I'd go with a machine putting out at least 25 cfm (roughly 13hp gas unit).

11-30-2006, 04:34 PM
so you really need 20 cfm, i was thinking you could get away with 12-14 and be fine. I guess ill have to shop around for a while to find one, maybe this isnt going to work out for me. What is it that i need to look for. Is tank size not really a big deal??, You would think that a 50 gallon tank would be able to put out enough pressure to blow out a line, but like i said im new to this.

11-30-2006, 05:18 PM
You can get away with less than 10 cfm, if you only have a very few jobs to do. But for doing any real quantity of work, you need to amp up the air quantity somehow. A larger tank is one way to increase the amount of air you send into a zone.

The old Speedaire in the picture lacks the one item that I still look for in my occasional searches for stuff to tinker with - that being the head unloader that allowed running it continuously with a gas engine, without needing any other controls. Newer ones use the air control line to lower the engine speed, while a relief valve vents excess pressure. When the old pump developed bearing trouble, I was able to use a larger replacement pump, and swap the cylinder head from the old one, and keep the head unloader. I think the pump is running cooler when unloaded, since it isn't actually compressing.

The other method I used to increase the air from a rig like that old Speedaire, besides using a larger engine, (they came with ordinary Briggs & Stratton engines, that always wore out) was to use a different pulley. An adjustable pulley lets you try different drive ratios and different cut-out pressures, to get as much useful performance as your engine can supply. You can obtain a mechanical tachometer to doublecheck the compressor pump speeds you obtain, to make sure you aren't straining the thing. The current time spent to charge up the tank-plus-hose is a minute to a minute-and-a-half, and that gives me enough air to handle rotor-head zones with 20 gpm flows. Larger rotor zones, and spray head zones, can require repeats. I usually use a pressure of less than 60 psi as a cut-off.

11-30-2006, 05:36 PM
By the way, if those links I've given aren't any good, it might be necessary to open the Grainger home page (http://www.grainger.com/Grainger/wwg/start.shtml?BV_UseBVCookie=no) first. Something about expiring cookies.

11-30-2006, 09:46 PM
Maybe this is a dumb question, but is their any way to figure out ratio's between tank size and and CFM. Also what is the recomended PSI to blow out systems with. Would a 50 gallon tank with a 100-150 foot of hose to the job, im not concerned with the time it takes to some extent, im not looking to knock out 100 systems a day.

Hank Reardon
11-30-2006, 10:17 PM
How many sites do you plan on winterizing per year? Just like shopping for a new mower, you need to match the equipment with the job. Sure you can mow an acre with a 21" but you'd be better off with a Z, right? The same thing applies here. How many sites could you realistically get? Are you planning on performing this service to only your lawn clients or more? It's a great revenue stream as most of your lawns are probably done anyway for the season. Before you go out an buy anything, you need to establish your goals for this new venture. Doing your homework now will reduce the risk of buying the wrong piece of equipment.

Sure, you may not really care right now that it would take you an hour to blow out a 10 zone system but I but after a season, my guess is you won't be happy with the results.

There is a guy here who winterizes with a small compressor and charges by the hour. On these small (+/- 10 zones) systems, the difference is I am up the driveway in 15 minutes or less (If I have a remote harness in the controller) for roughly the same amount. He's doing 10 a day, I am doing 10 before lunch. You can't do that without a tow-behind.

11-30-2006, 10:36 PM
CFM is strictly from the pump, and is ultimately limited by the horsepower (and torque) of the engine. The tank just stores air. More air storage allows you to deal with slightly larger zones, while requiring you to wait longer while the pressure builds up. Maybe now, the waiting won't bother you, but that can change. 30 gallons is about the practical limit on anything you're likely to see. A cheaper Grainger 30 gallon stationary (http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611627234)

You have to remember that these things are built with the idea of running air tools at about 90-100 psi, and that means a different 'drive ratio' than if you only want it to reach 60 psi. If tinkering with machines is not for you, you spend the extra money for a solid truckmount, that has a 12-13 HP engine on a 30 gallon tank. Then you just run the thing, and keep the outlet pressure under, say, 70 psi. Notice that these larger compressors have electric-start engines, and not all of them have the alternator to charge a battery, or a pull rope for manual starting.

12-01-2006, 11:05 AM
Long and Short of it, get a tow behind, I have a 125CFM that has paid for itself many times over and over. From my experience Lindsay makes a 80CFM unit and many IR 100 CFM units floating around my neck of the woods during winterizing season, and these will do residental systems with no problem. Kinda chuckle at the theory of doing installs and repair work correctly and effienctly[sp], but when it comes to winterizing they try to "Hodge Podge" something together. Remember the winter is long and usually extremely cold, and I want to know in the back of my small brain that all my systems have been properly winterized.

12-01-2006, 11:21 AM
Us tinkerers like to hodge-podge. Sure can't do a whole lot with computer-controlled truck engines any more. I doubt that there are many residential systems that a 25 cfm (or even smaller) truckmount can't handle with absolute certainty, but if there's room for a tow-behind, your dollar will go a lot further towards one of the many used ones to be had.

Without A Drought
12-01-2006, 11:35 AM
I've winterized with everything short of a bicycle pump. electric, gas, diesel, truck mounted, tow-behind. tow behind is my favorite, but price and manuverabitliy can make it less efficient. I also like the Kaiser sigmas, mounted in the truck. 20HP and 50CFM provided enough air to winterize 1000 resi's and some commercial last winter. Granted, i'm not doing golf courses or anything.

Personally, I need to get them done as fast as possible. i'll double up on the zones or run from the valves, anything to get out faster. ( i did 16 zones, soup to nuts, in about 5 minutes the other day). So i need somthing with those capabilities. If you only have a couple to do each year, have the time to spend running through them multiple times, letting the compressor recharge, and don't have visions of doing 20+ blowouts a day, you don't need too much. I would recommend the IR T30 or something around that. (But that's gonna cost you about $2000). Incidentally, I just listed a Gas Wheelbarrow compressor on ebay. I bought it last year just in case i needed something small and quick. I quickly realized it was a waste. i spent an hour winterizing a 10 zone system last december.


Dirty Water
12-01-2006, 11:45 AM
I've mentioned it before, we run two older compressors (much like the ones Boots is posted) mounted in our truck. They have newer honda engines, a 5 horse and a 8 horse with a 2-stage pump.

Tied together, they can winterize any residential just fine. Since we blow through test cocks here, your pretty limited as to the amount of CFM you can use anyways.

12-02-2006, 09:49 PM
I winterized the systems I had last year with a rented wheelbarrel style. the reason was to see if it would get the job done. 1" mains and average residential systems worked fine with the about 10cfm at 40psi that unit provided. If I find one a the right price, I'm going to buy it just to have for early and late season stuff. Now that I have sidelined my own stuff to punch the clock everyday again, I don't need much, but I have some clients that I can't refer to where I am now because they aren't in our service area. If your budget is $1000, a pair of wheelbarrels at 10cfm each in tandem would work. Cummins Tools had reconditioned ones with warranty for around $300 each. Brand new at Lowes or Cheapo for $600 each.

12-03-2006, 03:34 PM
Time is money , those electric and small compressors will work in a pinch or nice to have as a back up machine . But if it isnt pushing 30 cfm or more you are losing money due to innefficency . We can do 15 to 20 blowouts a day with our tow behinds , running 3 of them monday thru friday we do quite a bit .

A small wheelbarrow type compressor with a 5 hp motor to blow out sprinklers is about as efficent as using a shovel to install all your pipe .

A tow behind machine is something that customers notice , they see it and hear it , mine are loud for that reason , we have new customers come to us while we are out and ask us to winterize their system . They are great advertising mediums , place signs on sides and rear .

12-06-2006, 11:29 AM
Another good reason to favor a tow-behind is the ability to supply the needs of air tools, like a boring mole. I could tinker with my old Grainger until the next millenium, and it still couldn't supply a boring mole.

12-10-2006, 12:42 AM
Well, I finished the ones I had to get done personally today with a 15cfm emglo larger wheelbarrel model. For residentials, it was just enough. I had one zone with a broken line that I had to build pressure to clear, but I didn't have to tow anything either. I don't see any reason why 20cfm wouldn't be adequate for most residential work. I would really like to see some serious numbers on how much we actually push through a testc*ck. I've been towing a 185 all season and without jacking the pressure up, one zone is it in most cases. Give me a 3/4" threaded tee and I'll pop 6 zones at one time. In reality, how much time does that really save? 6 zone system at 2 min/ zone plus hook up, or 6 zones all blown at once plus hook up. When I am blowing a manifold, I still have the time to manually open and close those valves, so a 6 zone still take 4-5 minutes. 5 minutes plus hookup vs. 12 minutes plus hookup, but the machine costs less than $1000 instead of say 5K if we're talking new, or the machine costs 3-400 used instead of $1000 and it fits in the back of a small truck and you work those tight residential cul-de-sacs easier. That being said, I could never have blown 29systems in one day without the 185 (yep, I bungled the cake job and only got 29 on the first day, got the rest plus a tight route to make 26 the second day)

Dirty Water
12-10-2006, 10:08 AM
Using our two compressors (Combined CFM is probably around 35), we can do about 16 a day. Since we blow through test cocks, one zone max, pretty much regardless of the compressor size.