What compressor pump would be better for me?

[Flybyjohn]

I currently have an older Coleman Powermate 230v 15 amp 60 gallon tank single stage compressor. I have 75-100feet of 3/4 hose with high flow quick connectors on it. I use it for general garage stuff including impact gun , tire fill, blowing air, very rarely sand blasting and to blow out my sprinkler lines on 3/4 of an acre every year. The compressor works for me for everything but really works too hard during sand blasting and sprinkler blow out. I need more CFM.

I recently purchased a used industrial 26 amp motor for a great price off a pressure washer. I tested it and it runs but could use some new bearings. My plan was to get a McGraw 5 hp pump from harbor freight to use with my new motor to get better CFM for blowing out sprinklers.

It is rated for 15cfm @90psi. It is a two stage 175psi pump. I only have a 140psi W.P. Tank so cut off will be set to about 130-135 psi. I have seen a generic 3 cylinder single stage 5 hp pump rated at 22 CFM. It is about a hundred dollars more than the harbor freight but is advertised to make much more CFM. Acurate or not, I’m not sure. My tank is limited on max psi so I wont ever use the 175psi that the two stage is capable of. in my situation , would the single stage be better for my use or should I go for the two stage.

I am limited on money and my years left on this planet are dwindling so spending a lot of money on something that will last is not really a priority for me right now. This Coleman is on year 21 right now and what ever I get probably only needs to last another 15-20 more years.

 

[larry_g]

Given your details the single stage pump is what I would choose. That said I would question the integrity of the receiver/tank. 21 years on a consumer quality tank seems like a good run. Maybe consider getting a used compressor and when you need the volume of air connect them together for the specific job.

lg

 

[BillK]

I am not sure that a higher cfm pump is going to help you at all. Is there any way to shorten your hose length ? That is probably killing you more than anything. The higher pressure of the 2 stage pump will help overcome the resistance in the hose so I would definitely go that route if you do change.

You have to remember that the pump cfm only starts affecting you when the tank gets below the pressure you are using and the pump has to run continuously. I would not think that would be happening when blowing out sprinkler lines but I have never had to do that so I am not sure of the process.

 

[no704]

Check out Surplus Center.

 

[Flybyjohn]

BillK, I set the regulator to 50 psi when blowing out the sprinkler lines. To much more and I risk blowing a sprinkler valve. I use a 75’ - 3/4” garden hose to go from the compressor to the waterlines. I have up to 7 sprinkler heads each line that are 3-4 gallons a minute with water but with air probably a lot more. So that equates to around 25 gallons a minute @ 35 psi with water, not sure how many CFM that is using air after the initial water is blown out.

With my current tank I am stuck with a max tank pressure of 130psi so without purchasing a new tank, the useable 175 psi of the two stage won’t benefit me. So I would be starting with 130 psi with either pump. I shut the air off at 35 psi and let the compressor tank recharge with air again until it is full then give it another go. Each time more water is out of the lines and the tank has to fill the lines with pressure before the water starts getting blown out again. These lines are several hundreds of feet of 1” pvc and I also have 50’ of 2” pvc to fill before the sprinkler lines. I wanted no friction losses when I built the sprinkler system but that costs me when I need to blow them out. So the pump kicks on pretty quickly and then some water spits out until I get down to 35 psi again and the cycle starts over again. If I have more CFM then I have longer to push water mist before I have to cycle the pump off and on again. This might reduce the number of times I would have to fill the lines.

Doing some research it takes about a minimum of 20 CFM to properly blow out sprinkler lines. So the question is does the generic 3 cylinder single stage really have the CFM that it advertizes.

 

[Flybyjohn]

I just took a look at surplus center and it looks like it has some pumps that would fit the air supply demand but is quite a bit outside of my price point budget. If I wait for the right coupon from HF then I can get that one for around 200.00 or get the generic one with 22 CFM single stage for 349.00 from compressor source.

 

[Flybyjohn]

Larry-g, I have had my eyes open for a used tank for a while now. Can’t seem to find one at the bargain price for a once a year use. The only place I have to put the extra tank when not using it would be outside. Not sure how long it would last out in the weather. I did think I could mount it in the garage attic but it gets over 150 degrees up there in the summer. Still got my eyes open for one though.

I’m hoping to keep this minor upgrade to a very minimal cost. I got the motor for about 40.00 and will probably cost another 20.00 for generic ball bearings. That’s 60.00 and if I can keep the pump down below 300.00 then it will probably be worth not just calling in a sprinkler blow out guy with a trailer compressor once a year to blow them out.

 

[carlaisle]

Sounds like more storage would be more helpful than more pump.

 

[KenC]

Sounds like more storage would be more helpful than more pump.

I think I second this. Depends entirely on the duration of the 20cfm requirement. Just a few seconds, maybe up to 30, more storage definitely. Ideally, I would not want the compressor to be needed after filling the storage, just pump it up and dump the stored air into the sprinklers. Maybe isolate the irrigation field into sections to reduce the CFM needed.

 

[Flybyjohn]

Ok I’m hearing more storage. I’m still limited to 130psi max in the tank or tanks if I get another tank to add to it. My old pump now takes about 10-13 minutes to fill the 60 gallon tank from 35psi to 120 psi. Then it shuts off. I open the valve and the air rushes out and the pump starts again and runs for about 3 minutes until I’m back to 35psi. I shut the valve and pump until 120 again. The compressor runs pretty solid for about 3 hours until I get all 16 sprinkler zones blown out.

I can see how more storage would benifit me in almost every way and if I can find a cheap tank I’ll probable get it but I still need to buy a new pump to get the fill time reduced. I already have the motor ( just checked and it’s a marathon 6hp with 1.125” shaft) So the question still remains between a HF cheap 5 hp two stage or a cheap generic 1 stage that claims more CFM. Since I’m limited to only 130psi wouldn’t filling the tank up to 130 faster be a benifit? What would a two stage give me that a single stage wouldn’t if limited to 130 psi.?

So quick calculation would give me about 1 cubic foot of empty pipe I have to fill to 50 psi every time I turn the air on. The 60 gallon tank holds about 7 cubic feet of air. I can see how another 60 gallon tank would really help out here. So what should I buy for a pump to fill 120 gallons of air volume to 130 psi quickly and efficiently.

 

[Flybyjohn]

Update: I found a tank for 25.00 and spent another 20 to go pick it up. It was an old (1969) Ingersoll-Rand tank calculated to about 80 gallon size. The outside looked decent so I got it home and hydro tested it. It is rated for 200 and so I took it to 300 and it held over night. No leaks anywhere. The inside of the tank had a lot of oil residue and some rust so I made a rotisseri holder for the tank and the plan was to spin some gravel and degreaser to clean out the tank. I got the rotisseri built and spun the tank dry to begin and out came mucho amounts of rust. I wanted to see just how bad the inside was so I loaded it up with a coffee can of gravel and some oil eaters degreaser. Spun it for several hours and drained it. I then mixed up some homemade evaporust and spun 4 galllons for 12 hours. Drained and rinsed. Waited for night and stuck a flashlight inside on a wire to move to around inside the tank. Yes, it’s rusted and pitted inside. I went ahead and hydrotested it again with all the loose rust removed and it again held 300 through the night.

So where am I at? I know a tank can go any time but the question is, will it explode or let me know its time to replace it when a pinhole appears. If this tank is useable, at 80 gallon capacity @ 175 psi, it will be just about twice the volume of air as my 60 gallon @ 120 psi.

Just for fun I looked around at new 80 gallon tanks and holy cow, over a thousand dollars. Not in my budget right now or even in my next ten years. My thoughts are money for this one is already spent so get it set up for use and keep my eyes open for a tank in better shape and replace this one when I find one.

 

[Flybyjohn]

Photos of tank.

 

[nadogail]

IMHO, with a maximum pressure setting of 175 psi and a successful hydro test of 300psi any tank failure will be none catastrophic. You should first experience pin hole leaks and extended pump run times.

Failure of your pressure switch relief or valve will probably result in a serious problem.

 

[Flybyjohn]

I agree with failing pressure switches and relief valves causing catastrophic failures. Something I just started doing with my current compressor is turning the switch on when using and off again when I roll up the hose. I have just always left it on before but no reason too as the tank with the valve off holds air just fine.

 

[alwaysFlOoReD]

Photos of tank.

I like the rotisserie!

 

[Flybyjohn]

I like the rotisserie!

You would have really liked seeing it at 78rpms then. I pulleyed it down to a nice 40 rpm and it worked perfectly. I used the old bearings out of the compressor motor for the ends. They happened to be just about right size for the 3/4” and 1” pipes that went in the ends. A quick lick in the lathe is all it took. The bare tank was nearly balanced with half pound of weight. The balancing weight flew off at 78 rpm’s so I just left it off after reducing the speed down.

 

[KenC]

Ok I’m hearing more storage. I’m still limited to 130psi max in the tank or tanks if I get another tank to add to it. My old pump now takes about 10-13 minutes to fill the 60 gallon tank from 35psi to 120 psi. Then it shuts off. I open the valve and the air rushes out and the pump starts again and runs for about 3 minutes until I’m back to 35psi. I shut the valve and pump until 120 again. The compressor runs pretty solid for about 3 hours until I get all 16 sprinkler zones blown out.

I can see how more storage would benifit me in almost every way and if I can find a cheap tank I’ll probable get it but I still need to buy a new pump to get the fill time reduced. I already have the motor ( just checked and it’s a marathon 6hp with 1.125” shaft) So the question still remains between a HF cheap 5 hp two stage or a cheap generic 1 stage that claims more CFM. Since I’m limited to only 130psi wouldn’t filling the tank up to 130 faster be a benifit? What would a two stage give me that a single stage wouldn’t if limited to 130 psi.?

So quick calculation would give me about 1 cubic foot of empty pipe I have to fill to 50 psi every time I turn the air on. The 60 gallon tank holds about 7 cubic feet of air. I can see how another 60 gallon tank would really help out here. So what should I buy for a pump to fill 120 gallons of air volume to 130 psi quickly and efficiently.

Being limited to 130 means that there is no real benefit from a pump being two stage. But, CFM is the key. So I'd buy all the CFM both my budget and motor will support. Some two stage pumps offer more CFM than some single stage, but not all. You will have to do the math with pulley sizes, rpm, pump displacement etc to determine what the best buy would be.