Is UK tap water safe without a filter?

Public drinking water in the UK is regulated and tested to standards a domestic filter is not required to meet. People filter for taste, for the smell of chlorine, or to reduce limescale in a kettle - not because the supply is unsafe.

Does a filter jug soften water?

Not in the sense a softener does. A jug filter reduces some of the hardness minerals in the water it treats, which is why a filtered kettle furs more slowly, but it does not soften the water reaching the rest of the house.

What does a carbon filter actually remove?

Activated carbon is good at chlorine and at the tastes and odours that come with it, and at some organic compounds. It is not a barrier to dissolved minerals, which is why carbon alone does not address hardness.

How often do cartridges need changing?

The manufacturer sets an interval by volume or by time, and it is worth keeping to. A cartridge left in past its life stops helping and becomes somewhere for bacteria to grow, which is the one way a filter can leave water worse than it found it.

Water filters for the home

Most people who filter their water in the UK are doing it for taste rather than for safety, and that is worth saying at the top because it changes which product makes sense. Public supply here is regulated and tested; a filter is a preference, not a precaution.

The four kinds, and what each is for

The filter jug

A carbon-and-resin cartridge in a jug. Cheapest to start, no plumbing, and by far the most common. Good for chlorine taste and for slowing kettle scale. The running cost is the cartridges, and over several years that is the larger number — which is the thing the shelf price does not tell you.

Tap-mounted

A small unit that screws onto the tap and diverts flow through a cartridge. No jug to refill and no plumbing, but it fits only some tap designs and slows the flow while it is engaged.

Under-sink

A plumbed cartridge under the worktop, usually feeding a separate small tap. Higher upfront cost, larger cartridges that last longer, and nothing on the worktop. Needs installing, and needs the cartridge changing on schedule by somebody who remembers it is there.

Reverse osmosis

The most thorough domestic option: water is forced through a membrane that holds back the great majority of dissolved substances. Two costs come with that. It sends some water to drain for every litre it produces, and it strips beneficial minerals along with everything else, so some systems add a remineralising stage back in.

Filtering is not softening

These two get sold into the same conversation and they solve different problems. A softener treats the whole house so limescale stops forming in the plumbing and the appliances. A filter treats water at one tap so it tastes better. Neither substitutes for the other, and a household in a hard-water area that only wants nicer tea needs the cheaper one.

Judging the running cost

The honest comparison across all four is cost per litre filtered over the life of the device, not the purchase price. A jug is cheap to buy and the dearest per litre; an under-sink unit reverses both. Work out roughly how much filtered water the household actually gets through in a week before choosing, because that number decides which way round the answer comes out.

On specific removal claims

Filters are marketed on lists of what they remove, and those claims vary by cartridge and are testable. Water Pages will publish a comparison when it has read the manufacturers' own test data rather than their packaging, and it will cite which standard each claim was tested against. Until then the descriptions above stay at the level the mechanism supports.

Common questions

Is UK tap water safe without a filter?: Public drinking water in the UK is regulated and tested to standards a domestic filter is not required to meet. People filter for taste, for the smell of chlorine, or to reduce limescale in a kettle - not because the supply is unsafe.
Does a filter jug soften water?: Not in the sense a softener does. A jug filter reduces some of the hardness minerals in the water it treats, which is why a filtered kettle furs more slowly, but it does not soften the water reaching the rest of the house.
What does a carbon filter actually remove?: Activated carbon is good at chlorine and at the tastes and odours that come with it, and at some organic compounds. It is not a barrier to dissolved minerals, which is why carbon alone does not address hardness.
How often do cartridges need changing?: The manufacturer sets an interval by volume or by time, and it is worth keeping to. A cartridge left in past its life stops helping and becomes somewhere for bacteria to grow, which is the one way a filter can leave water worse than it found it.