Filter media are consumed as they work. That is the whole principle: KDF-55 converts chlorine by giving up part of itself in a redox reaction, and activated carbon fills its pores with the compounds it adsorbs. Neither can be recharged at home. Once a cartridge is spent, water passes through it essentially untreated.
Which makes cartridge replacement the single most important thing about owning a shower filter, and the thing most people forget.
The short answer
Roughly every three months for a normal household. That assumes two people showering daily at typical UK flow rates.
What moves that number
- How many people use the shower. A cartridge is rated by volume of water, not by calendar time. A family of five will get through one considerably faster than a single occupant.
- Your water hardness. Hard water areas load the sediment stages faster.
- Shower length and temperature. Long, hot showers use more water per session.
- Pipework age. Older properties push more rust and sediment through the pre-filter stages.
How to tell yours is finished
You do not have to rely on the calendar. Three signs, in the order you usually notice them.
- Flow drops. The most reliable indicator. A loaded cartridge restricts water. If pressure has fallen off gradually over weeks, that is the cartridge, not your plumbing.
- The chlorine smell comes back. If a hot shower starts smelling faintly of a swimming pool again, the chlorine-reducing media are exhausted.
- Soap stops behaving. Shampoo that suddenly needs two goes is worth noticing.
A trick that actually works
Write the date on the cartridge in marker before you fit it. It takes two seconds and it removes all the guesswork three months later when you are standing there wondering. If you would rather we remind you, email us your purchase date and we will set one up.
Changing it
Water off, unscrew the housing anticlockwise, lift the old cartridge out, drop the new one in the same way round, check the O-ring is clean and seated, screw the housing back hand tight. Then flush for 30 to 60 seconds; the first run may look slightly cloudy as loose carbon dust clears, which is normal.
Do not reach for a spanner. Overtightening crushes the O-ring and causes exactly the leak it is supposed to prevent.
Can you clean and reuse one?
No. You can rinse visible grit off the outside of a mesh pre-filter, but the KDF and carbon stages are chemically spent. Rinsing them does nothing. A cartridge that looks clean can be completely exhausted.
Full step-by-step instructions are on our installation page, and replacement cartridges for every VORASSO product are in the shop.