Vacuum Pump + Bag Build Log

Hello everybody! 

I’m loving this new theme of build threads, and i was inspired by user Lavarat to come up with my own. I’ve been following the aging hipster build for a little while now, and it finally pushed me over the edge. I wanted to make a vacuum setup. 

As always with me, it’s on the cheap! Practically free! FREE!!

So to begin, a little something to know about vacuum setups. Lots and lots of people use a repurposed Freon pump. However, a proper vacuum pump can be had for about 100$ new, even better models can be had even cheaper on eBay and craigslist. I am a project junkie, i love to tinker; and im always tight on cash. This is a very effective and cheap way to do this and it was a lot of fun to make. I encourage anybody who wants to do this however, to read up on circuitry, currents, and general electrical work if you are uncomfortable working with electrical parts. 

Types of Freon compressors-

Scroll, Piston, Vein, and Diaphragm. I have been told scroll is the best. I have made a piston type in the past and it seemed to work just as well though. They are all very even. The scroll and vein will be SLIGHTLY louder. A whisper louder in my case. 


Where to get your compressor-

You can get yours in any appliance that uses phase changes, or Freon. Things like air conditioners, Fridges, Mini Fridges, humidifiers, Dehumidifiers etc. 


My build 

I had been hunting around for a discarded fridge or AC unit, but no dice. So i went to my neighbor’s house and asked if they had anything that was broken or not used anymore. Luck would have it they did! A medium sized dehumidifier they bought a long time ago that hadn’t worked in years. I felt around the copper lines in back and nothing was cold, i also found a small crack in the rear of the condenser where the Freon had drained out. I took it all apart and cut the copper lines outside on my lawn. A tiny amount of Freon was still left inside. After the pump was liberated from the casing i removed the main PCB, capacitor, and all the left over wiring which i got to use later when i made my wiring harness. 

I drove to Lowes and picked up a coil of 1/4ID vinyl tubing (5$) 2x 1/4 barb fittings (5$) a junction box and a few screw in connectors to tighten all the wires in (1$) and some thread sealing tape and putty (5$) A grand total of 16$ for a vacuum pump. Not too shabby. 

I mounted the compressor and the junction box on a small piece of wood with the rubber feet that were in the original unit. I copied down a wiring chart for the pump on an old pizza box and did my wiring according to that. It’s a three phase pump, add takes a starting current to get the motor running. The leads to the head of the pump were labeled, C, R, S, for common, run, and start. The common in the three prong cable was tied to the common on the pump, the hot was tied to an old toggle switch i had then to one side of the capacitor. From the same side I tied the hot cable to the “run” lead on the pump.  With the last lead on the pump, the “start” lead, i ran that to the opposing side of the capacitor. I then grounded the whole thing to the body of the pump. After buttoning up all the wiring and stuffing it all into the junction box, it was good to test. The pump cycles from its starting cycle to its run cycle automatically with a flip of the toggle. 

I took my tubing and pushed it onto the suction side of the pump and used a small hose clamp to secure it. The pump had little to no oil in it, so i dipped the suction end of the pump into some compressor oil and let the pump suck in a little oil. 

It runs hot naturally, as there is no Freon in the loop to cool the pump. I don’t run it for long periods of time. It’s used to draw a vacuum, then the bag is sealed off and the part of left to cure. No continuous run. 



  • If you have a single phase pump, you will not have nearly as many steps. Just follow the wiring diagram on the pump directly to the wall. Always include capacitors and resistors in the circuitry around the pump. 
  • If your leads on your pump are not marked, use a resistance gauge to test them. The lowest resistance will be your common and run. The Middle resistance will be your common and start, and your last and highest resistance will be the Run and Start. Draw a little diagram with the wire colors labeled, and find the common wire. Tie that wire in and wire around it to finish the pumps wiring. 
  • BE SAFE!!!!!! I made a mistake before on the first pump i made, and it was disastrous. A huge arc of electricity went from the harness to the body of the pump. Always ground you and your work. Never ever work with anything plugged in. Always cover open connections.
  • To cover difficult areas, use plasti-dip. Stuffs rad. I dipped my whole capacitor in the stuff with the wires attached as well as the bottom of my switch. Watertight and safe to touch even when current is running through them. 

In my next post I hope to cover more of the plumbing and making the vacuum bag. 


Thanks for reading



Very cool, cheap is good, free is better… keep em coming…

As i was playing around with the pump, flattening bottles and stuff, it was getting much to loud and hot. I did a little digging and found the capacitor and pump will automatically switch from Start cycle to run cycle, but only as a reserve measure. So i decided to wire in a switch onto the starting relay to allow me to turn on and off the starting circuit. Not only does this solve the noise problem, but i can now start my pump even when it’s under a full vacuum. Rad. 

I moved my new vac out to the shed where it lives on its own cabinet. I also got some work done on the vacuum bag. It worked so well i even tested it out on a custom weed graphic center fin im making for a buddy. I laid up about 35 layers of 4oz and let her cure out in the sun (suncure). After it was good and solid i cut out 2 1/8" thick panels of light wood out to the shape of the panel. I brushed on a liberal amount of resin, laid on both playwood panels with one layer of 4oz on either inside of each panel, and tossed her into my bag. 

The switch on the left controls the starting current, and the switch on the right controls the overall power to the unit. If you only turn on the power, the pump will not start. You turn on the power, then engage the starting current to turn over the motor, then disengage the starting current after the motor has started. 

The Bag Build-

I found some large roll of the plastic you wrap new furniture in at the dump. Pulled it out of the heap and brought it home. It’s twice as thick as a heavy freezer bag and stretches very well. I cut out a square about 14" x 14" and laid it onto a piece of sheet metal. Using some double sided window tape i also got at the dump, i made a little bag just big enough for the fin panel to fit into. I drew a vacuum and it was perfect. No leaks, no tears, nothin. For my breather cloth im using paper towels folded up and tapped together with basic office tape. For the valve stem, well i don’t have one. Unfortunately a nice reusable vacuum valve stem i cannot make. Ill most likely buy one from

Also in the works is a homemade resin catch-pot. A bunch of resin was sucked into my vacuum line, cant have that! Until i get that done, im not sure how to keep resin from entering my vacuum line. 

As for a complete board bag and tape, im all set. Pretty soon ill embark on that journey. But for now im happy just making some fins. 

Thanks for reading



Big day today on the vacuum pump build!

Got home around 11:30 from exams and got to work. I made up a vacuum chamber out of leftover PVC and air cannon parts. Glued her up and tapped the hole for the 1/4" barb fitting on the side. 

I got a call from my sailing coach asking about the windsurfing boards im going to be repairing for the school, and while we were in the shop i spotted a box labeled West System Vacuum Bagging Kit. I asked my coach if they ever vacuum things and he said they used it a number of years ago, and i could scavenge stuff from it if i needed anything as they don’t ever use it. SCORE! I ended up grabbing a few rolls of tacky-tape, some gasket tape (the gas rated stuff) and a spare vacuum gauge. 

Drove home and installed the vacuum gauge into my chamber, closed the valve, and let her run. To my surprise my little pump drew 27Hg! Way more then i thought it would. 

I also calculated the CFM of the pump, it evacuated a 2.2ft^3 @ 27Hg in 20 seconds.  27/30 = .9        .9(2.2) = 1.98            1.98(3) = 5.94CFM of vacuum. Of course this rate slows as the vacuum starts to work under more load. 

I also came up with a little idea on a bag entry! Using an old tire schrader valve from the dump, i drilled out the center. I poked a small hole in my vacuum bag (heavy zip-lock bag for testing)  and stretched the valve through. Next i slid a soft rubber grommet over the valve neck and bag that is just slightly smaller then the rubber neck on the valve. The rubber on rubber is a perfectly airtight seal. I used an old bike pump end and put the hose end on the vacuum chamber, and clamped the locking connector onto the schrader valve. Pulled a full vacuum of 27Hg no problem. Turned off the pump and let it sit for about 30min, still no leaks! 

Thanks for reading


Hi Angus, for a simple bag entry, skip the tire valve and just cut a small hole in one corner of the bag, stick your hose in there and use an inch or two of that tacky tape to seal it up. If you make or buy a reusable bag closer then a roll of tacky tape will last a for a whole bunch of bags.

the bag closer is like a giant Zip-lock: you can buy them or make one by cutting a plastic pipe into a “C” shape and finding a piece of rubber hose that fits tightly into the “C”.

for bags I just use 2-4 mil plastic sheeting, cut to double size, fold it in half and tape two of the three open edges with cheap masking tape. Use the bag closer on the third edge.