Vitamin C shower filter or KDF: which media to buy for your water

The two shower filter media worth buying work in completely different ways, and the right one depends on a fact about your water supply that your utility publishes. Here is the difference and how to choose.

How each one works

KDF stands for kinetic degradation fluxion, a trade name for granular copper-zinc alloy. Chlorinated water passing over it sets up a redox reaction: the alloy gives up electrons, free chlorine takes them and becomes chloride, the same ion that is in table salt. The alloy is consumed very slowly, so a cartridge lasts months. It works in hot water, which is why it beat activated carbon as the shower media of choice. Its weakness is chloramine, the chlorine-ammonia compound some utilities use; KDF reduces it only partially in the time available.

Vitamin C, as ascorbic acid or sodium ascorbate, reacts directly with both chlorine and chloramine. The reaction is fast and complete, which is why ascorbic acid is a standard dechlorinating agent: aquarium keepers use it before adding tap water to a tank, and utilities use it to neutralise chlorinated water before releasing it from flushed mains. In a shower filter it works instantly and at any temperature. The cost is stoichiometric: every milligram of chlorine uses up vitamin C, so the cartridge is literally dissolving as it works and runs out in weeks rather than months.

The comparison

Bunnings prices checked 21 October 2026. Running costs are our estimate from 4 October 2026.

Which disinfectant do you have

This is the only question that matters, and the answer is on your utility’s website.

Chlorine: Sydney Water, Water Corporation (Perth), Icon Water (Canberra, which states that chloramine is not used), TasWater (Hobart), Power and Water (Darwin), Hunter Water (Newcastle), City of Gold Coast (whose 2024–25 report says its network is chlorinated), Unitywater’s Sunshine Coast and Noosa zone (its published results show free chlorine with monochloramine below detection), and most of Melbourne. Buy KDF.

Chloramine: Seqwater’s grid where it supplies Brisbane, Ipswich, Logan and Moreton Bay, SA Water’s metropolitan Adelaide supply (its glossary explains chloramine is used in longer distribution systems across the state), and Melbourne’s western and outer growth zones. Buy vitamin C. Our city pages summarise each.

If you are not sure, a pool test strip that reads total chlorine will show a residual under the shower in either case; the difference is that a KDF filter will bring a chlorinated supply to near zero and barely move a chloraminated one.

The combined cartridges

Amazon AU lists many cheap filters with both KDF and vitamin C inside, usually in “15 stage” or “25 stage” housings. In principle the combination covers both disinfectants. In practice the quantity of each medium in a $27 cartridge is small, the vitamin C is used up first, and you cannot see how much of either remains. We have not added one as a pick because none we looked at states how much KDF or vitamin C it contains. If you buy one, treat it as a two-month cartridge and test it.

What neither does

Soften water, remove fluoride, or do anything to skin and hair that we can verify. Both reduce chlorine; vitamin C also reduces chloramine; that is the honest end of the list. The do shower filters work guide goes through the evidence, and the hard water shower filter guide deals with scale.

The picks

KDF: the Philips 3-stage filter. It is the reputable KDF unit sold here, with replacement cartridges on Amazon AU, and it is the right buy for the majority of Australians on chlorinated supplies.

Vitamin C: the Quoss universal filter, because its refills are easy to get: Bunnings sells them as a Special Order, like the filter, and Amazon delivers them. A vitamin C filter without refills to hand becomes an empty tube within a season. The Sonaki cartridges on Amazon AU are the refill for anyone with a Sonaki housing, and their listing names chloramine. The Bunnings shower filter guide lists everything else Bunnings sells.

The one trap

Buying vitamin C because it “does more” when your water is plain chlorine. It does, and then it runs out in two months, and you are paying $20 to $25 a cartridge to do a job KDF would have done for six months. Vitamin C is the right answer to chloramine and an expensive answer to chlorine. Check the utility first; it takes two minutes and decides the next five years of cartridges.