I just replaced my shower filters, so I thought I’d update my best shower filter review from earlier this year. Each update to the review generates a lot of useful comments. So I’m incorporating what I’ve learned from those comments into this latest review.
Why filter your shower? Well, because your skin is really good at absorbing things. For example, about 60% of the chlorine that is absorbed daily comes from showering in chlorinating water. Because most of us shower under tap water, we absorb things like chlorine, chloramines, heavy metals and VOCs through our skin on a daily basis. Ideally, we’d like to get rid of all of those contaminants. But that’s really only possible if you filter the water as it enters your house using a whole house filter. So most of us are stuck with filtering water at the showerhead, and that’s not optimal. In a shower, the water moves fast and it’s under high pressure. This makes filtration difficult. Also, the water is typically hot, which makes filtration difficult too.
Let’s now look at the three main types of shower filters: KDF (Kinetic Degradation Fluxion) Filters, Carbon Filters and Vitamin C filters.
KDF Filters are by far the most popular shower filters in the U.S. KDF filters remove free chlorine by reversing the electrochemical process that originally separated the chlorine from sodium in a brine solution. However, KDF filters suffer from two major limitations: they don’t perform well in hot water, and they don’t remove chloramines. Chloramine or NH2Cl (a combination of chlorine and ammonia) now commonly being used in place of chlorine for disinfection. This is because chloramine does not dissipate as easily as chlorine. But this also means it is harder to remove from water. Even the best KDF filters can’t remove chloramine, but they are reasonably effective at removing chlorine. KDF filters last about 6 months. The best rated KDF filters are made by Aquasauna and Sprite.
Carbon Filters are useful for removing certain organic chemicals and chlorine in cold water. Chlorine is attracted to and held (absorbed) into the surface of the carbon particles. However, the efficiency of absorption is basically nullified when the water becomes warm. When used in a showerhead, activated carbon is only effective for a short time — the filter gets clogged quickly by sediment in the water.
Vitamin C Filters are commonly sold in Asia, but they are difficult to find in the U.S. Vitamin C filters are simple — they contain a large block of Vitamin C (ascorbic acid), and water runs through the filter and comes into contact with the Vitamin C. The Vitamin C neutralizes about 99% of the chlorine and chloramines in the water. Vitamin C filters last about 6-12 months, and their effectiveness does not diminish until the Vitamin C is used up.
Here are the chemical equations:
When Vitamin C reacts with chloramine, the byproducts are dehydroascorbic acid, ammonia, and chloride (beneficial to the body).
When Vitamin C reacts with chlorine dissolved in water, the byproducts are dehydroascorbic acid (another form of vitamin c) and hydrochloric acid (in minute quantities).
A fellow who goes by the alias ReviewGuy did an independent test of the different shower filters, you can read about his results here.
Vitamin C filters are really the only type of shower filter than works consistently, especially if your water contains chloramines. Unfortunately, many Vitamin C filters are cheaply made. Here’s my review of the different products available:
Sonaki Vitamin C Handheld Showerhead Chlorine Filter
The Sonaki Vitamin C Handheld Showerhead Chlorine Filter has the best build quality I’ve found. It costs about $90, and it comes with a low-flow showerhead. The showerhead has two spray patterns and an off switch. I like the feel of this showerhead, and the fact that the filter is transparent, so you can see when the Vitamin C has run out. It also comes with two replacement Vitamin C cartridges. It’s available from Amazon for $90.
Sonaki VitaMax Vitamin C Inline Filter
The Sonaki VitaMax Vitamin C Inline Filter is a good choice if you already have a showerhead you like. This filter fits in-line and works with your existing showerhead. It costs about $50, and it’s available from Amazon.
In my home I currently use a Sonaki inline filter attached to a Culligan shower filter (this is an expensive charcoal shower filter). This combination looks makeshift but it works quite well once installed. The Sonaki filter is for chlorine and chloramine removal, and the Culligan filter is to remove scale, rust and other contaminates.
Update: Here’s a study on ascorbic acid and chloramines.
Thanks to Darren and SteveG for their research.