From the outside, a shower filter looks simple: a cartridge in your shower head. Inside there are usually several layers, each with its own job. But what exactly do those layers do, and what can a shower filter not do? Besjaar explains, without the marketing talk.
The short answer
Water flows through a few filter layers one after another. A mesh holds back particles. Other layers break down free chlorine or bind substances. A shower filter does not make your water softer: the water spends far too little time in the filter for that.
Why a shower filter is different from a water filter
A filter jug in the kitchen has all the time in the world. The water drips slowly through the filter, and it is cold. In the shower, things are different:
- The water is warm. Some filter layers work less well at high temperatures.
- The water flows fast. A shower easily delivers 8 litres per minute or more. The water spends only a very short time in the filter.
- The filter is small. Only a limited amount of filter material fits in a shower head.
That is why you cannot expect the same from a shower filter as from a drinking water filter.
The filter types at a glance
| Filter layer | What it does | Honest note |
|---|---|---|
| Mesh or sediment filter | Holds back particles, such as sand, rust and loose limescale particles | Does not remove dissolved substances from the water |
| Activated carbon | Binds chlorine and some odour and taste compounds | Works less well in hot water and can then release bound substances again |
| KDF (copper and zinc) | Breaks down free chlorine through a chemical reaction | Actually works well in warm water, but only on free chlorine |
| Calcium sulfite | Breaks down free chlorine, also in warm water | Gets used up over time, so it needs replacing |
| Vitamin C | Neutralises chlorine very quickly | Gets used up, so this filter also needs replacing in time |
| Maifan stone and ceramic balls | Often added for minerals or a softer feel | Little independent research exists; treat them as a side issue |
| Ion exchanger (resin) | Can bind limescale | In tests, not a single shower filter lowered water hardness |
Which layers work in warm water?
With ordinary activated carbon, warm water is a weak point. As early as 2000, the trade magazine WaterWorld wrote that carbon is not recommended for hot water, because bound substances can be released again at shower temperature. KDF and calcium sulfite are designed for warm water. According to the maker of KDF, a KDF shower filter removed 96 to 100% of chlorine at normal shower temperature in tests, and less in cooler water. Note: those figures come from the manufacturer itself. Vitamin C reacts very quickly with chlorine, according to the US Forest Service (USDA).
What a shower filter cannot do
- Soften your water. Dissolved limescale stays in the water. In an independent test by Water Filter Guru, not a single shower filter lowered water hardness. If you really want softer water at home, you need a water softener. See water softener or shower filter?
- Make your water safer. Dutch tap water is already safe. A shower filter is about comfort, not health.
- Cure skin complaints. A filter is not a treatment for eczema or other skin problems. See hard water and dry skin.
How the Besjaar filter works
In the Besjaar Shower Head with Filter, water flows through a filter with eight layers, including calcium sulfite, maifan stone and ceramic balls. The calcium sulfite breaks down free chlorine. That mainly matters when your water has been treated with chlorine, as in Belgium, France and Spain. Dutch tap water normally contains no chlorine, read is there chlorine in Dutch tap water?
A filter gets used up over time. Replace the Besjaar filter every 3 to 5 months, depending on how often you shower. The Besjaar Replacement Filters come in pairs. You will find all filters in the Besjaar shower filters. Not sure whether a shower filter is for you? Read shower filters: worth it or not? first.
What to look for in a shower filter
- Which filter layers are inside? A good manufacturer names them. Against chlorine in warm water, KDF, calcium sulfite or vitamin C are better suited than carbon alone.
- How long does the filter last? And what do replacement filters cost?
- Does the pressure stay good? A filter should not noticeably throttle the spray.
- Certification. There is an American standard for shower filters, NSF/ANSI 177. It tests how much free chlorine a filter breaks down in warm water. But few shower filters have that certification.
- Honest promises. Be wary of filters that promise to soften your water or cure skin complaints.
Frequently asked questions
Does a shower filter make your water softer?
No. Dissolved limescale stays in the water. A shower filter can hold back particles and break down free chlorine.
Does a carbon filter work in the shower?
Less well than in cold water. In warm water, activated carbon can release bound substances again. For the shower, KDF, calcium sulfite or vitamin C are better suited against chlorine.
How often should you replace a shower filter?
It differs per filter. A Besjaar filter lasts 3 to 5 months, depending on how often you shower. Replace it sooner if the spray becomes weaker.
Besjaar makes shower heads and filters for Dutch bathrooms, from Assen. Better water, every day.
Sources
- Water Filter Guru – Do shower filters work?
- WaterWorld – Ricci (2000), Media is a big thing, but not the only thing
- Kymera International – KDF shower filter test (manufacturer)
- USDA Forest Service – Using Vitamin C to Neutralize Chlorine in Water Systems (2005)
- WWD – New NSF standard verifies shower filtration product claims (2004)