Is there anyone that makes a refillable carbon filter I can use inline with my sawyer filter to remove chemicals? Platypus makes a filter but it's not refillable. Bulk carbon is far cheaper than the 13 dollar platypus filters. They aren't something I want to buy a ton of.

You might have to make your own...not a bad idea as the Platypus is the only current one I've found (I have an older Sweetwater/MSR inline one); and their disposable, not reusable.  

ROCK6

I found one made by Katadyn. It's a bit larger diameter than I'd like but it should work.

If you run some searches we got into making them in a reverse osmosis thread I think.  Don't recall if they had their own thread.



PVC pipe and buy the carbon in bulk from fish supply places, I think that was best place to buy it but as usual I forget.



Anyway, you can make it how you want it and even paint it pretty colors.  

I bought a Sawyer Gravity carbon filter to put in line with the Sawyer Mini.
my mistake, I think it is a Platypus Gravity filter.
I was a little disappointed in how small it was (and expensive for what it was; but good for my immediate use and pack size).
I was thinking along the same ideas; considering if a fuel filter would be threaded to disassemble and filling it with coconut husk activated charcoal.
The next size up looks like a water filter self-contained cartridge @ 6" long and 1.5" in diameter.

Found this, maybe it'll work:     Mr. Gasket 9706 Universal Clearview Fuel Filter   < $6
     Spectre Performance 2369 Universal Clear View Fuel Filter   < $10
     Earl's 230103ERL Fuel Filter < $36