By The Zagosa Team. Published .
Reviewed or updated .
Ask a mineral cartridge to run your tub single-handed and it will let you down. What silver and copper cartridges actually do is cut your sanitiser demand by around half and leave the water feeling nicer. Every serious tub maker still pairs them with a small residual of chlorine or bromine, and if someone claims otherwise, they have a product to sell you.
What the metals really contribute
Silver ions kill bacteria at a slow, steady pace across a broad range of temperatures. The catch is that they do nothing to oxidise organic muck, which is the second job any sanitiser has to cover.
Copper holds back algae and adds a bit of extra bacteriostatic effect. That is why mineral-cartridge tubs tend not to turn green even when they sit unused for a while.
What neither metal can do is react to a sudden spike. Put eight people in the tub for a garden party and the cartridge is overwhelmed well before the afternoon is out.
The jobs still left to you
Hold a low residual: roughly 0.5 ppm free chlorine or around 1 ppm bromine. The minerals cover the slow baseline; the conventional sanitiser handles the surges and the oxidising.
Shock every week with a non-chlorine oxidiser. Skip it and organic load creeps up, and the cartridge gradually stops earning its keep.
Swap the cartridge on the maker's timetable. They are not magic. Once spent, they release nothing at all, and the only clue is your sanitiser demand quietly doubling.
Where cartridges earn their place
Households with sensitive skin. Halving the chemical residual halves the dryness and the odour along with it.
Tubs that see gentle, occasional use. A slow, constant release suits a quiet tub far better than the on-demand hit of neat chlorine or bromine.
Hard-water postcodes. The minerals compete for surface adsorption sites and give you a small but genuine hand against scale.
Common questions
Do they pair with bromine?
They do, and the mix is gentle and steady. Run the cartridge with roughly a 1 ppm bromine residual alongside it.
Could the cartridge stain the shell?
Only if copper drifts too high. In soft-water areas, check copper at every refill when a mineral cartridge is in use.