Using filter stack in bi-directional flow system

So I am doing final prep for a bi-directional extraction and ran into a few questions. Mainly, what’s the best way to safely run both ways through a felt filter.

At first I planned to just stack the 4 felt filters (75, 25, 10, 1 micron) on top of a steel sintered plate with a perforated plate on top. would that work? Would the depth of the felt allow for lateral movement and thus reduce the need to space filters out?

I cut a few mesh sizes of diesel filter into disks that are 3", and 4" (for a 2.9" inner diameter spool). Should I use the 4" and use c-clamps, or is it okay to use 3" between a couple of sintered plates. It seems like the plates would prevent fluid from bypassing the filters and keep the filters in place regardless of flow direction.


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Maybe consider multiple filter stacks, and some have a plate on top of a ring so you can use 2 layers of filtration on each filter stack!
And if you’re wanting them on a bi-directional then maybe get 4 filter stacks, 2 on each end, so there is space between each layer of filtration

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you’re thinking about your plumbing wrong.

go through the flower in both directions.
go through your filters in one.
(go through dewax in one direction, go through CRC in one direction)

otherwise anything you catch is spit out into your product when you go “backwards”.


Have solvent entering at bottom of system, but above filter stack.

I have several extra sintered disk/filter stacks laying around to use, I’m hoping to reduce parts/complexity/heat-transfer where possible though. If using felt instead of paper/steel filters is it likely that spacing is less important? Sometimes I get hung up on one factor/feature to the exclusion of others, maybe this is one of those times.

Thanks @cyclopath
I have a system like this, which appears to inject through the filter on top, and has none on the bottom.
I bought 2x 3"-1.5" reducers so I can add 3" filters under the Injection port and valve, would that make sense? On top, where would I buy a part to bypass the filter stack?
I am not using dewax, just a sleeved material chamber and cryo solvent. I’m also holding off on CRC until I have more knowledge and experience. So if I get the filters sorted everything is good to go!

I have a theory on now to simplify this but it would require putting my 3" sight glass on top of the material chamber at eye level. If that isn’t a safety concern I would just bottom fill until I see solvent through the sight glass, and then immediately flush/dump it all through the bottom valve like a normal top fill. Would that be a reasonable approach?

Put your crc just above the ball valve going to your collection pot then just run like you normally would unless I’m missing something.

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Post a pic of system will help to see what u have setup already


nice rack!

is really the MISSING part if one wants bi-directional flow and CRC.

@Idab916 OP pointed us at this critter

@JazzBandit you could certainly put filters at both ends of your column. I suggest you look at racked systems to understand how to best achieve your goals, especially long term ie: adding CRC.

you don’t want to build a monstrosity along the lines of subzero (pre CRC)

Looks to me like @StoneD started with gear similar to what you have. Then he went to a rack so CRC wasn’t stupid. (Guessing)

Others resort to nailing stuff to the wall.

(You might want to explore that entire thread…)


Rack mounting was best thing I ever did…saves my back plus I don’t have a tower I gotta climb in chair or step ladder just to reach the top the material column. God I don’t miss lifting that monstrous rig. Not to mention I no longer have to worry about it falling over due to being top heavy!


Hi Jazz,
The potential problems in stacking different microns like this (one on top of the other) is as another person pointed out, you should have some space in between. So a stainless disc with large holes would help. The problem arises the particles will start to accumulate on the surface and it has no where to go without space. The other potential issue is if you have large numbers of particles in one of the micron ranges you are using is that micron layer will plug much faster than the others which are hardly used.

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Use something like this above filter stack


@cyclopath, I read the thread you suggested and got a great understanding of different philosophies that have had success.
Haha, and some of those towers are scary to imagine operating, maybe just because of my lack of experience. I have an overhead cable because I was afraid of such a tall skinny tower of a machine. It looks like mine isn’t even that tall! I was planning to make a 1-meter diameter three-legged “teepee” type frame, but the wall mount with hard lines is a more attractive option. I appreciate the suggestions :+1:

@StoneD , I did a few runs yesterday and today and while swapping that splatter platter I feel what you are saying about your back! Time for me to mount this kit to something.

Thanks @Filterman9 that helps me understand how to think about this. I’ve definitely seen thick layers accumulate on filters while winterizing with a Buckner filter. I got a couple of ring/plate sets and will make use of them :point_right:

That looks like a quick and affordable solution @Idab916 , thanks for pointing it out!


75 Um is pretty big (“holes”). coffee filter is about 25. Seems like if you don’t have spacers that provide free lateral movement than you could place a 75um between each layer in your stack or double layer each of your felts. But I wonder if you’re over thinking it.