The complete guide
Hard water in the UK, and what a jug can honestly do about it
Around 60% of the UK lives in a hard or very hard water area. If you are one of them, the chlorine taste is probably not your main complaint — the kettle is.
What hardness actually is
Hard water is water that has picked up dissolved calcium and magnesium on its way through chalk and limestone. It is not a contaminant and it is not a health problem; it is a nuisance with a chemistry.
When you heat hard water, those dissolved minerals come out of solution and deposit as calcium carbonate — limescale. That is the crust on your kettle element, the film on the inside of the glass, and the scum that floats on tea.
Hardness is measured in milligrams per litre of calcium carbonate:
| Classification | mg/L CaCO₃ |
|---|---|
| Soft | 0–100 |
| Moderately hard | 100–200 |
| Hard | 200–300 |
| Very hard | 300+ |
Broadly, the south and east of England are hard to very hard; Scotland, Wales, the north west and the south west are mostly soft. Your water company publishes the figure for your postcode, and it takes about a minute to look up.
How ion exchange works
Activated carbon — the media in almost every filter jug — works by adsorption. Organic molecules and chlorine stick to a vast internal surface area. It is excellent at taste and odour and essentially useless against dissolved calcium, which does not stick to carbon.
Softening needs a different mechanism. Ion-exchange resin is a bed of small beads carrying loosely-held ions. When hard water passes through, the calcium and magnesium ions swap places with the ions on the beads. The hardness stays on the resin; the water leaves softer.
The catch is built into the mechanism. The resin has a fixed number of exchange sites. Once they are all occupied, it stops working. A plumbed-in softener gets around this by regenerating the resin with brine on a cycle. A jug cartridge cannot — so it is a consumable, and hard water consumes it faster.
That is why this cartridge is rated for about a month while our carbon-only cartridges run for three. It is not a worse filter; it is doing a harder job.
What a jug will and will not fix
It will help with: the taste and mouthfeel of drinking water, scum on tea, the rate at which your kettle scales up, and cloudiness in hot drinks.
It will not fix: scale in your boiler, shower head, washing machine or dishwasher. Those run on the whole-house supply, and nothing you pour into a jug touches them. Anyone promising otherwise is overselling.
If whole-house scale is the real problem, a jug is a partial answer and a plumbed-in softener is the actual one.
Practical habits that help
- Descale the kettle anyway, monthly in a very hard area. Filtered water slows scale; it does not abolish it.
- Do not leave softened water standing for days any more than you would ordinary water.
- Prime a new cartridge by running the first couple of fills to waste, which clears resin fines and stops the first glass tasting odd.
- Change it on time. An exhausted ion-exchange bed is not neutral — it simply stops softening while you carry on believing it works.
If softening is not your problem
Most of our range is carbon-based and aimed at chlorine, taste and odour rather than hardness: the Lucid jug is the cheapest way in, and the ED01B is the same idea with a pump. For genuinely comprehensive reduction including dissolved solids, reverse osmosis is the only thing in this catalogue that gets there.