Top flood, bottom flood or?

Hello everyone…brand new here and happy to have the opportunity to learn and participate.
Brand new to bho extraction and very interested in getting my first bho setup…
After some research…several questions have come up…Considering purchasing a turn key unit(or close to it) and some of the units I’ve looked at have bi-directional flooding(?) of the column…Any advantage to this feature…?..

Any and all advice would be much appreciated…
Thank you all for taking the time to read this…

I do a bottom fill then flush from the top. I think the bottom fills the column completely no channeling then flush it all out from the top


Thank you for the response Ganjatan…
I’m still trying to figure out a few things before I start buying equipment…every bit of info helps…

Won’t a valve under top flow do the same?

Just curious, but at temp should it matter

I worked for an extraction company for years. All their stock units were designed for top flooding, but they also had parts available to accommodate bottom flooding as well if customers desired.

All the managers and engineers continually said they were fairly sure there was no difference. I personally have also run a few different extractors in my day, and if there is a difference, I have never noticed it because it was too insignificant.


Thank you for the information StoneD and GandalfTheGreen…
I need oil for editables and I’m trying to figure a unit to start with and not waste time or money…
Best I can figure…I’d need to run a 5 pound colum 30 times a month to cover current needs…
I still not sure if piecing something together is the way to go…or purchasing a complete turn key unit…
Thank you again for the info…

For that amount piece iT together and have @Killa12345 help You out with the design even a terpenator design gets the job done with a 12" collection pot
And a 4" blast tube
Buy a couple of extra blast tubes and end caps
Place material in the tube
Cap the tubes and pull full vac
Place in freezer and once frozen run them


Really appreciate the info Roguelab…
I read myself in circles…and…so much info in this industry can be less than reliable…
4200 has a wealth of info…and… it’s great to have people willing to point in a general direction…
Roguelab…placing the tubes in a freezer…Is a -80 C freezer the way to go…or…overkill…?
Most of this is very new to me…
Thanks again for the patience…!!!


I Don’t have a ton of experience with bottom flow but from what I have read and heard from others is that if you feed from the top your solvent will try and take the path of least resistance to make it through. If you flood from the bottom it will do a better job of covering the full surface area of your column and pull more heads. Someone shut me up if this is incorrect haha

Once again, what about top flow w valve under material column?

Is it not exact same thing just reverse?

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i always did top flow with a valve underneath, but only because I soak for a bit. Column under full vac, it sucks the solvent in until it’s full… Especially if you’re running cold and everything is under vac, it fills before it builds any pressure. In my mind it’s the same concept to prevent any channeling

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Yes a -86C freezer is wise watch for internal height of the freezer to place the tubes standing often 48" don t fit
If You set freezer temp at -60 C the freezer has a bigger freezing power
I yust keep iT at -86 C

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Bottom feed isn’t necessary. Oil for edibles? Perhaps alcohol extraction may be better for you. Cheaper and easier.

It prob will do the same, I have done it top flood and bottom flood, I think I get slightly better yields from the bottom, I only hav a 1.5 x24" tube so I need every last drop lol don’t we all ha

That thin I don’t think your having any channel issues…

I think that applies for something a lil larger.more wide


I have noticed (sumtimes) that wen I fill from top with the valve closed at the bottom to let soak for an hour wen I open the top valves and tank valve more solvent comes out in to the column b4 opening the bottom

This MAY be true. But only if you’re doing a wash, not a fill and soak. And probably only with larger material tube sizes. If it’s a fill and soak, you’re gonna be soaking everything even if it channels while the tube is filling.


When the extractor preforms a first wash, top injection, the cannabinoids at the top of the column will be extracted at a rate that is faster then the cannabinoids lower in the vessel are brought into solution. So, even if you top injection and soak, as the cannabinoids and solvent are drained from the column, oils may be redeposited in the bottom of the vessels material. Thus for secondondary washes it may be advised to fill from the bottom to re dissolve the redeposited oils. Not my preference, as I prefer countercurrent extraction vs batch (flood, spray or backflow solvent wash)


Interesting :grinning:Care to explain the counter current part !!

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Thanks to everyone for sharing their knowledge…countercurrent extraction…sounds interesting…I still have soooo much reading and work to do…
How difficult is it to outfit a column so it can be flooded from the top or the bottom.?..
I know certain bho equipment sellers advertise this feature…