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Can I Regenerate Used Water Filter Carbon?

There are quite a few claims going around that spent carbon can be regenerated / re-used.

We've looked into this carefully and have come up with the following:


Can I Recharge the used Water filter Carbon by... washing it in bleach?

No. The Activated Carbon used in water filters is made by treating raw carbon/charcoal with oxygen. This makes the carbon more porous and able to absorb more chemicals.

Used carbon is already ‘filled’ up chemically. Contrary to myth, soaking used carbon in bleach won’t make it work again.

Bleach / chlorine is one of the easiest things for carbon to absorb so you are literally just absorbing more bleach . All you would be doing is adding to what the filter has already filtered out.


Can I Recharge the used Water filter Carbon by... washing it in a salt / saline solution.

There are disputes about this ie the idea that soaking used carbon in cold salt water for several hours… then cold (salt-free) water for several more hours, will make it work as new.

We’ve looked into this in detail and tried it ourselves. Our conclusion is that it does have some effect but it’s limited.

If the process is done correctly the resulting recharged carbon doesn’t filter nearly as well as new carbon. And the process will only work one or two times.

It seems the myth about recharging using salt perpetuates because it does work for *some* water filter media eg “Zeolite”.


Can I Recharge the used Water filter Carbon by... washing it in hydrogen peroxide?

Yes. But be careful. Hydrogen peroxide is a very powerful chemical… Here is a method that reportedly works:

1) Dry the used carbon in air and sunlight for 48 hours

2) Soak in normal hydrogen peroxide for 24 hours. This kills the bacteria (likely the biggest contaminant in the carbon)

3) Rinse carefully with water and allow to dry completely ie 24 hours

4) Place the carbon in baking dish and bake at 450F for one hour.

As you might note this is quote a lot of effort and isn't exactly "green". But needs must...


Can you regenerate/reactivate the carbon by Heating it?

Yes if you can heat it to 800 – 1000 degrees Celsius in an Oxygen free environment. This will burn off contaminants and reactivate the carbon. But this isn’t possible in most domestic settings - a microwave won’t do it.


Checkout Other things you can do with used water filter carbon


Go back to Main page about recycling water filters

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