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Refilling carbon filters

148 posts in this topic

If in the UK theres a company called AAC Eurovent , they supply various grades of activated charcoals for repacking canister filters and also supply plastic repackable canisters as well as steel ones along with a whole host of other air in &  venting related products.

Edited by Dodgee
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Until I started a lockdown grow last year, I hadn’t quite appreciated the degree of pong attenuation that would be required.  Pretty much everything I used in the grow - medium, lights, fans, heating, nutrients - was improvised or scavenged, at least to begin with. 

Same went for the filter; I saw enough videos about activated carbon (boy, would I like to get a pyrolysis conversion fired-up!) to understand how and why it works and the conclusion was simple - build my own filter.  The long and short of it is that some garden centre 12mm mesh, a pair of tights, a plastic paint can, a 4” aluminium fire extinguisher (since replaced with 4” pvc pipe), sticky tape and a tube of silicon were soon fashioned into concentric tubes with space for 8, I think, litres of charcoal...which, of course, I wanted to make myself.  That’s a whole ‘nother story - detailed in the thrilling tales of my En-suite dreams thread last year.  I did eventually lose faith in my home-activated carbon, though it turned out to be a small by-pass air channel left when I closed the filter originally.


Meanwhile, I refilled it with some AC from an aquarium supplier.  Coconut shell, 5kg for 26.99, eBay.  The important point is that this AC was NOT in pellet form, ie. not wet extruded from a machine, but was crushed to size.  If you’ve done some basic reading on the value of AC and why it works, you’ll understand why this distinction is crucial.   In the same way that charcoal briquettes are formed from what is, basically, dust - pellets don’t have the exposed internal structure of crushed and graded charcoal.  Thus, they’re cheaper but expire faster.  Any loss in performance when venting a stinky flower will become noticeable, unlike a marginal loss in a restaurant air system.


Just because the one I used was sold for aquarium water filtration makes no difference - what’s important is that it is hardwood charcoal that has been activated, then crushed and graded to a suitable size.  The fine particles probably go to pellet makers.


Ask yourself why a charcoal briquette is noticeably heavier than the equivalent lump of natural charcoal and that, in turn, is heavier than a piece of activated charcoal.  The AC has soooo much more surface area exposed as all you’re left with is the structure of the wood with all the channels clear and accessible to the air passing through.  If pellets have been processed as a slurry, you’ll grasp why they are so much less effective.


Filter carbon should be considered a consumable and routinely changed, there’s too many people making money from expensive, useless filters with cheap carbon and this site’s rife with disgruntlement about it.  

So, refill and keep refilling as regularly as necessary (with the good stuff, which is surprisingly clean to handle) then even a disappointing filter will keep working.


Here endeth the lesson.

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I did this for a project, took exactly 3kg out, could only fit 2.6kg back in. No matter how I tried, couldn't get the same amount in. Same sized pellets too. My thinking is that pellet density is important, as the filter was never quite as good with some smell leakage. It's also impossible to know if the carbon is already spent, ie, we getting old pellets from an industrial chemical labs.. (mind you, how do we know new filters aren't using old pellets). 


To pack more in, I think it would need some heavy duty vibrating, as just pouring the stuff in and shaking ain't gonna cut it. 


I now save time and sanity by purchasing the best I can afford as soon as the smell comes back. In my case a 6" and 4" Phresh 300mm, and 4" intake filter to prevent bugs getting sucked in. Still cheaper than a lawyer, and apart from noises, the most essential purchase to prevent needing a lawyer in the 1st place. :yep:





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Not strictly related to re-filling, but to rejuvenating - After being totally out of the game for a while, I'd decided to start a few seeds off indoors under CFL and LED to bung outside to finish, but they started getting a bit too tell-tale smelling even in veg. I dug out 2 ancient long sized 6 inch Ikon filters, ended up sucking through one next to the plants and blowing out through the other, and although that took most of the smell away it provided a rather strong 'old filter' smell of its own.


I had a couple of small filters kicking about I'd found dumped. I emptied one into a couple of baking trays and bunged them in the oven at 250C for an hour ish. Now I know it takes much higher temps and an inert atmosphere to properly reactivate it, but I hoped if I just got it hot enough to drive off a lot of the volatiles, I figured I may get a bit more use out of it.


It stunk the place out whilst doing it, but not too bad and not remotely like canna, and bunging it into the end of the ducting with the 6 inch RVK on it, well it now takes care of the veg smell all on its own and it's only tiny!


Based on these positive results, I busted open one of the big Ikon filters and leaving the net inside, I filled 3 deep oven trays with the contents, then put them in the oven on full again, propped some windowns open and nipped out to get some self-tapping screws for the reassembly...


When I got back some 30 or so minutes later the whole street stunk and there were visible fumes coming out the windows. It smelled like a fire in an enamel paint facility or something but again fuck all suspicious TF, but it was fecking awful, choking and tear inducing.


I flew all doors and windows open grabbed a small extraction fan and some 4'' ducting and rigged it up in the kitchen, retired to outside.


Next door closed all their doors and windows, I was getting to be a bit of a nervous wreck - windown ceaner and bin men arrived, and I didn't know where to fucking look! Anyway after a total of about 2 hours I quit and turned off the oven. Shoulda taken about another 2 but this had drained me already.


Anyway, got everything calmed and cooled down, and started wondering what the hell caused the smell like that?!? Then I remembered outside of my care it had spent some time in a factory unit and they'd been doing *tons* of paint spraying there during that time. FUCK!


Anyway, put the damned thing back together this a.m. will test it out when I regain the will to live, use some essential oils for a good test. Will post how it goes heheheheh...


So yeah I'd fully rec. doing this in the household kitchen 101%


P.s. FUCK!


P.p.s. I got all the carbon back in no problem, just taped the netting out the way, closed off the inner tube with a towel in a bag, taped cardboard high round the outer, then just poured it in and poked it down with a long flat ended 6mm dowel.



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@Slippy One how did it dgo - did your mini regen in the oven work?


@FlowwolF could you message me a link to the seller you used for the crushed activated carbon on ebay 


Im having odour issues in veg stage after only 2 months, I might give this ago rather than replacing the whole filter as need to watch the pennies.

I seem to think mine has screws but will have to check,  if not, its only drilling out the rivets and getting some self tappers.

I just need to get the right filter medium.

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Has anyone ever taken a rhino pro apart?


The screws are in a different location to most filters. I’m wondering if they’re glued at the top?

I’m not looking to refill I want to repurpose it. A rhino pro is for sale locally. 

Edited by Kev.k

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I finally got round to refilling my old filter, a 100mm x 250mm swiftair filter.


These where slightly different as it had 2 lots of rivets on the top section - on the neck and around the edge. The ones on the neck, held the inner mesh cylinder and the outer ones the outer main body. With the Top hat end off I poured out the spent carbon.

They also  had a fine mesh netting inside the main cylinder and on the exterior of the inner cylinder. these weren't fitted very well originally, so I taped the bottom of the material and made a bag - this then lined the inside of the main cylinder.

I then taped round the bottom edge of the internal metal cylinder, attaching the netting to it.

Pushed it home inside the main body and then filled it up using 4mm aquarium activated charcoal (carbomax)


A few photos to show what I poorly explain above lol 


Rivets - upper ones where already ground off and were knocked out with a punch, the lower heads were drilled out with a 5mm drill bit and pulled out with a pair of pliers



inner and outer fine netting sandwiching the activated carbon granules - I didnt think it smelled much but Im nose blind to weed






netting "sock" made into a bag 



mesh netting open sock on outside of inner cylinder taped around bottom - this gives it a really snug fit when its pushed down onto bottom "cone" 



I clipped to top of the inner net to keep the carbon out of the central void, then refilled it with 2 kg of the 4mm carbomax 



original "chips" where between 2 and 5mm



with the filter filled, the netting was turned in and over the carbon and the top taped to keep it packed nice and tight.

I actually had to use a bit of the old carbon to top it up level with the outer cylinder, as you can see the volume of 2kg pellets was less than 1.6kg of chips



Top fitted back on and fixed in place with 4 gauge x 1/2 inch self tappers - tools only did old school measurement self tappers 



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@RUFUS HOUND Very interesting read there mate, and great to see the pics, and details of how you went about this, excellent stuff, and fair play :yep:


Would there be much of a saving in just buying the carbon to refill like you've done here, compared with buying a new filter, thanks :thumsup:

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All depends on the price of the activated carbon but I would say youll save 30 to 50% on the price of a new filter.

IMO I believe we have a duty to repair / reuse rather than the throw away society we find ourselves in,  my carbon cost £15 and new filter of that size would be £30 at least. 

If theres nothing wrong with the casing, you just need to replace the carbon and its an easy job =  no brainer for me!


yet to test it as just put on a new filter on the tent, which enabled me to have a crack at this used one. cant see me getting another filter from now on I'll just replace the carbon.


amazone have a 3L bucket of the chips rather than the pellets (which Im going to order) for just over £11 :shock: bargain (25% off currently) search for:

Supa Filter Carbon 3 Litre Bucket, Suitable for Aquariums/Fish Tanks And Koi Fish Pond Filters, Improves water clarity by removing contaminants


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the slight error I made was not realising the pellets are heavier than the chips for the same volume.


so even though I removed 1.6kg of chips and replaced with 2kg of pellets, the vol was still a little less but now others can learn from my error and thats what its all about.

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@RUFUS HOUND Thanks mate, that sounds good :yep:


lol Have to agree there, it's a bit of a mad balancing act though, i've just spent a grand on new grow equipment,

but apart from socks, and jocks, i've bought all my clothes from second hand shops now for 12 years, and i used to be

the worst for buying new brand names that you could ever meet, but ya every little helps :thumsup:

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@RUFUS HOUND, cracking job there mate. :yep: Great documentation too.


I have three of those filters, bought them each as part of a bundle with cheap 100m fan and ducting. Will certainly keep your process in mind when they start to be less effective. Mind you I'm at 16 months usage of the first one, and no problems so far. Reckon they're good for 18 months/2 years, depending on how much moisture they need to absorb. I push air through them so maybe they get a slightly easier life... :) 

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Posted (edited)

Thanks @Crow River I was doing it anyway and just thought Id share and take a few photos along the way - we are all in this together and if it helps 1 person thats good enough for me.


most carbon will be ok upto 70% RH, mine lasted a good 18 month of continuous use, same bathroom fan 100mm running no stop and it still as good as when it went in - sods law dictates that it will now breakdown.

ps the 3L bucket of carbon also has an extra 15% off subscribe and save for first order so at £9.50 odd I bought one for next time.:thumsup:

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