TheVacuumGuy's guide to building a multipurpose vacuum pump.

[TheVacuumGuy]

Multipurpose vacuum pump

by the VACUUM guy



What?


Vacuum pumps are a quite expensive beast, plus a lot of care has to be taken to not break it due to gasses, acids and so on.

In this guide I’ll describe how to build your own, for a fraction of the costs, and has added benefits:

• performs very reasonable. could boil water in room temperature
  
  
• it is chemical resistant
  
  
• it is capable to pump out/over fluids (from your reaction mixture, or water from a hot/cold bath
  
  
• could be used as a gas scrubber.
  
  
• Reaches a low enough pressure to boil water at room temperature.
  
  
• Control the strength using a knob.

​	Temp F​	Temp. C​	Microns​	inHg​	PSIA​
WATER BOIL​	212​	100​	759,968​	0.00​	14.696​
DEVICE AVG​	76​	24.44​	22,860​	29.02​	0.442​
DEVICE MAX​	59​	15​	12,700​	29.42​	0.245​

Required materials​

1 - A water pump. Don’t go cheap on amazon! Pay some more for good stuff!

Ensure it is 12v (or 24v). Go for higher pressure over higher throughput. Throughput of around 5 to 8 L/m is sufficient. But pressure should be at least around 5Bar/80psi. The amazon pumps break within the first week. Those more expensive pumps will last years! ( and i’ve pumped nearly everything (bromine, piranha solution, etc). The pumps also don’t break when dry.

.

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2 – A plastic box, like curver or something.
Recommended to take higher model. Dimensions on average:
w: 30cm x d: 35cm x h: 40cm

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3 – Hosing . Don’t go cheap either. I took a EPDM gasoline hose with inner size of 10mm. Around a meter or 4 leaves you some room for error.

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4 – Water jet pump. Or ventauri pump. Should cost you not more than €50. Choose PTFE!
make sure it has an adapter with it, so you can replace the screw connector with a “hose connector

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5 – Power supply. This can be (unlike point 1), perfectly bough with Amazon. Ensure you have the best Amperage, so 30V-10A instead of 60V-5A or 120V-3A

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6 – Optional , but which is what i’ve done. Some rack

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7 – Wiring and vacuum hosing (silicone for example) 10 mm. And hose clamps (the one with a wingnut are most convenient)

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“Schematic” side view​

The rack from the side , with the motor underneath on the floor.

On the first tray comes the plastic curver box.

on the second tray comes the power supply unit.



The curver box can be easily emptied by just pulling the 2 hozes out of it and
pull it out. Then with fresh water you push it back in and let the hoses come back into the water.


- When a real low pressure is needed, you can put it on steroids by adding a load of icecubes to the water.
- You can add Sodium Bicarbonate to the water to work as a neutralizer
- You can use the vacuum line with some adapter to capture the output gas of your apparatus instead of a hose to outdoors.

DO NOT ALSO use this for cooling your condensers!

 

[Osmosis Vanderwaal]

Whay kind of venturis do you use? When I was looking at them it seemed like your choices were $20 for a plastic one, or $300 for a scientific brand-name metal one

 

[TheVacuumGuy]

Ptfe one . Like so

 

[Osmosis Vanderwaal]

I wondered if the plastic ones could pull a usable vacuum, and yes they can. Glass and metal aspirators can REALLY PULL A VACUUM if you use ice. I saw a plastic asperator could achieve 150mm/hg ( atmospheric pressure is 760 mm/hg) and some expensive ones can pull down to 50mm/hg, -13.7 psi. I think you mentioned not cooling the water, but the vapor pressure of water determines how much vacuum it can pull, so cold water would make it pull harder, but I don't see a reason you would need that

 

[TheVacuumGuy]

I did mention ice for real power. I built mine 14 months ago and I've used ice 2 times (for testing). Why would I need to go sub millibar ?

With metal ones, try pumping some acid through it and see what happens.

And glass one is not for me. I'm the guy needing to weekly order some glassware that I broke

All in all, this works perfectly for nearly all use cases. Actually I use it the most to pump water from my reaction mixture, or pump the mixture itself to another flask. And of course vacuum filtration. And all this without the need for all sorts of traps



Here are the details of this plastic unit I have . 16/24 mbar is more than sufficient imho for a home chemist.

And the water consumption is 0 since you recirculate it

Water consumption approx. 190 l/h at 3.5 bar flow pressure
Suction capacity approx. 400 l air/h at 3.5 bar flow pressure
Max. vacuum at 3.5 bar water pressure approx. 16 mbar at +12 °C
approx. 24 mbar at +20 °C
Length of water jet pump with R3⁄4″ connection approx. 210 mm