Buying carbon by the bag rather than in a cartridge is what owners of media vessels do, and it is a different exercise from picking a filter off a shelf. You are specifying a material, working out how much the vessel takes, and then doing a physical job that is heavy, messy and easy to get wrong in ways that show up months later as poor performance.
Specify the media, not just the word carbon
Ask for three things. The base material, since coconut shell and coal based carbons have different pore structures and suit different targets. The form and grading, because pellets, granular and fine mesh behave differently in a bed and the grading determines pressure drop and backwash behaviour. And whether it is catalytic, which matters enormously if chloramine is the target: standard carbon reduces chloramine slowly and incompletely, while catalytic media is made for it. Buying generic carbon and hoping is how a freshly reloaded vessel underperforms the one it replaced.
Work out the volume before ordering
Media is sold by volume, typically in cubic foot bags, and the vessel takes a specific amount plus an underbed of gravel where the design calls for one. Order from the manufacturer's figure for that vessel rather than estimating from its height, and remember the bed is not filled to the top: freeboard above it is what allows the bed to expand during backwash, and a vessel packed full will push media out to drain. Order the gravel underbed at the same time if it is being replaced, and buy one spare bag rather than stopping halfway.
Loading without damaging the distributor
The riser tube and its lower distributor are fragile and central to how the vessel works. Tape the top of the riser closed before pouring anything so no media falls down it, hold the riser upright and centred, and use a wide funnel. Load the gravel underbed first if there is one, gently, so it does not crack the distributor, then the carbon. Take the tape off before fitting the valve. Anything that ends up inside the riser will end up in the household plumbing, and a broken distributor means media in the taps and a vessel that has to come apart again.
Backwash to waste before it goes into service
Fresh carbon carries fine dust, and the first water through will be black. Put the vessel into backwash and run to drain until it runs clear, which takes longer than people expect, and only then return it to service. This also settles and classifies the bed properly. Note the load date, since carbon exhausts invisibly and the schedule is the only thing telling you when it is spent. Our carbon media replacement guide covers removal of the old bed and how exhaustion is judged.
Questions people ask about carbon pellets
How much media does my vessel take?
Use the manufacturer's stated volume for that vessel, plus the gravel underbed if the design has one. Do not estimate from the tank height.
Should I fill the tank to the top?
No. Freeboard above the bed is what lets it expand during backwash. A vessel packed full will send media out to drain.
Does chloramine need a different carbon?
Yes, catalytic carbon and much longer contact time. Standard carbon reduces chloramine slowly and incompletely.
Why is the water black after loading?
Fine dust from fresh media. Backwash to waste until it runs clear before putting the vessel back into service.