Vacuum size vs flask size

Sorry for the beginner’s question but I cant seem to find a straight answer about this.

If I were to run a very VERY small spd setup, say using a 250 or 500ml flask, would I still need a higher CFM pump to obtain proper vacuum or could I get away with a cheaper 3 stage or less? I cant seem to figure out if the flask size (or I guess overall volume within the setup) will have a determination on the size of pump that I’ll need to reach proper vacuum. Im assuming it does. but I cant seem to verify that or find any specifics.

I’m just looking to make disty from my couple of plants a few times a year for personal use. Not super concerned about a 100% perfect double distilled product by any means, just want to make something out of my trim that’s decent and safe.

I’ve made crude from an entire harvest of trim before and only ended up with 150ml of oil after winterizing and decarbing and with my plant limits that wont really ever change so all these 1000 or 2000 systems im seeing would just be complete overkill.

Any suggestions would be great, thanks everyone.

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Necessary vacuum power scales with total volume of system and the amount of gases being generated per (unit of time). small boiling flask, small system, you won’t need a terribly powerful pump.
as an example, we use a Welch CRVPro 16 (12CFM) on a 20L short path system with success (though, we use two in tandem and only use Short Paths for decarb/degas–we do NOT use them for cannabinoid passes, though we could if we chose to). if you’re scaling down to 500ml you can scale CFM down fairly proportionately.

as far as flask size, the heating mantle would define that i think? unless you meant you’re still choosing the mantle/flask size; you probably don’t need to go much above 1000-2000ml for personal use IMO

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Thanks so much for your reply.

The entire setup that im envisioning (lol dont laugh too hard) is a 250ml flat bottom flask on my magnetic hot/stir plate with a cheap amazon head that pulls vacuum from the head itself (right after the condenser) instead of a cow. To change fractions I’ll attach small 50-100ml round flasks to the end of the head directly as I come to temp. I’ll use an ice bath, circulating pump and hopefully a cheap amazon vacuum.

I know this sounds ghetto AF. I really dont mind spending a little money to get something proper but I just dont really see a ton of options or SOPs for something of this small scale so im kinda left to DIY a bit and most of what im finding just wont work with the volume im doing.

Totally up for any other ideas anyone else might have.

That is not advisable and not Good Laboratory Practice. Breaking vacuum and allowing air to com in contact with the hot distilland is Bad Practice.

Invest in a distillation receiver.


This is good to know thank you. Potentially saved me a nasty burn.

I had a feeling this wasn’t a great idea but didn’t think about that.

Do you have suggestions on something like a cow receiver but on a much smaller scale? I saw someone using a cow but it had sealed “vial” like ends to it (sorry I know I’m showing my inexperience here) but I’ve never been able to find those or know what they’re called.

Chemglass has most everything you will need and will serve you well in the 250 mL to 1000 mL range.

In addition to a good vacuum pump you will need a good vacuum gauge and good temperature control.

I can help you with all that. Feel free to DM me.

Actually just found this on eBay and I think this is pretty close to what I’m envisioning with a bit bigger flat bottom boiling flask

However… and correct me if I’m wrong please. This is put together backwards isn’t it?

Yes, that is assembled backwards.

I do not recommend that type of distillation glassware. Stuff like that is mostly used in academic research when only dealing with very small quantities of distilland.

You will need at least 24/40 joints to be able to fill and empty flasks without too much hassle.

Check Search results for 'CFM liter' - Future4200

Very few NEW questions…but figuring out how to find the answers without the correct jargon can be non-trivial

@beaker had a mantle that takes a 250ml flask

He also had one with a 50ml flask…

@Roguelab has the smaller